Wellcome!

 

 

Asked/Added Questions From NCERT:


Question 1. Asked on :26 September 2020:06:02:58 PM

Explain why some  oils spred on water, when other float as drops.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Isf surace tension of oil is less than that of water, then it spread on water.

-Answered by Shruti Srivastva On 26 September 2020:06:04:16 PM


Question 2. Asked on :26 September 2020:05:59:54 PM

Water gets depressed in a glass tube whose surface is coated with wax. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The angle of contact between water and wax is obtuse. So cos Θ is negative and hence cappilary rise.

-Answered by Shruti Srivastva On 26 September 2020:06:01:15 PM


Question 3. Asked on :26 September 2020:05:57:46 PM

 The split in the tip o the nib acts as a capillary tube. The ink rises up in the nib due to capillary action. Hence we are able to write with the pen.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

nisha sheikh
The tip of the nib of a pen is split in order to provide a capillary which helps the ink to rise to the end of the nib and enables it to write continuously.

-Answered by nisha sheikh On 22 October 2020:06:37:45 PM


Question 4. Asked on :26 September 2020:05:56:04 PM

Why new earthen pots keep water cooler than the older one? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Due to cappilary action.

-Answered by Shruti Srivastva On 26 September 2020:05:57:04 PM


Question 5. Asked on :26 September 2020:05:54:06 PM

A piece of chalk immersed in water emits bubble in all directions why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Because it has a large number of cappilaries.

-Answered by Shruti Srivastva On 26 September 2020:05:55:36 PM


Question 6. Asked on :26 September 2020:05:51:56 PM

Why undergarment are usually made of cotton? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Cotton threads have large number of cappilaries between them. These capillaries help to absorb sweat from the surface of the body due to capillaries action.

-Answered by Shruti Srivastva On 26 September 2020:05:52:32 PM


Question 7. Asked on :26 September 2020:05:49:32 PM

Why sand is drier than clay?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Due to narrow pores in clay, water rises in the clay due to capillary action and keeps it damp. Practically no pores or capillaries exist in sand and hence water cannot rise in sand. So sand is dryer than clay.

-Answered by Shruti Srivastva On 26 September 2020:05:50:13 PM


Question 8. Asked on :26 September 2020:05:47:17 PM

How does the cotton wick in an oil-filled lamp keeping on buuring?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The narrow spaces between the threads of the wick serves as cappilary tubes through which oil keeps on rising due to capillary action.

-Answered by Shruti Srivastva On 26 September 2020:05:48:19 PM


Question 9. Asked on :26 September 2020:05:45:03 PM

How does the cotton wick in an oil-filled lamp keep on burning?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The narrow spaces between the threads of the wick serve as capillary tubes through which oil keeps on rising due to capillary action.

-Answered by Shruti Srivastva On 26 September 2020:05:45:53 PM


Question 10. Asked on :26 September 2020:05:42:41 PM

How does the plouging of feild help in preservation of moisture in the soil? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
THis is done to break the tiny capillaries through which water can rise nad finally evaporate. The plouging of field helps the soil to retain the moisture. 

-Answered by Shruti Srivastva On 26 September 2020:05:43:51 PM


Question 11. Asked on :26 September 2020:05:40:47 PM

What does make water proof raincoat water proof? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The angle of contact between water and the material of the raincoat. So the rainy water does not wet the raincoat.

-Answered by Shruti Srivastva On 26 September 2020:05:41:27 PM


Question 12. Asked on :26 September 2020:05:38:17 PM

Teflon is coated on the surface of non-sticking pans. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When the surface of a pan is caoted withteflon, the angle of contact between the pan and the oil used for the frying purpose become obtuse. Thus the frying pan becomes non-sticking.

-Answered by Shruti Srivastva On 26 September 2020:05:39:15 PM


Question 13. Asked on :26 September 2020:05:36:11 PM

What is the importance of water proofing agents? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
They are used to increase the angle o contact between the fabric and water to prevent the water from penertaing the cloth. 

-Answered by Shruti Srivastva On 26 September 2020:05:37:01 PM


Question 14. Asked on :26 September 2020:05:34:10 PM

What is the imporatnce of wetting agents used by dyers? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
They are added to decrease the angle of contact between the fabric and the dyer so that the dye may pentrate well. 

-Answered by Shruti Srivastva On 26 September 2020:05:35:10 PM


Question 15. Asked on :26 September 2020:05:29:58 PM

Two soap bubbles of unequal sozes are blown at the ends of a capillary tube. Which one will grow at the expends of the others and what does it show? 

-Added by Rohit Rajput Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The bigger one will grow at the expense of smaller one. This is because excess pressure is inversely proportional to radius and air flows from higher pressure two low pressure. 

-Answered by Shruti Srivastva On 26 September 2020:05:32:31 PM


Question 16. Asked on :25 September 2020:06:25:50 PM

Why excess pressure in a soap bubble is twice the excess pressure of a liquid drop of the same radius? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
A soap bubble has two ree surfaces, one internal and another external; whereas liquid drop has only ones outer free surface. 

-Answered by Shruti Srivastva On 25 September 2020:06:27:04 PM


Question 17. Asked on :25 September 2020:06:23:52 PM

The paints and lubricating oils have low surface tension. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The paints and lubricating oils having low surface tension can spread over a large surface area. 

-Answered by Shruti Srivastva On 25 September 2020:06:24:52 PM


Question 18. Asked on :25 September 2020:06:21:35 PM

The addition of flux to tin makes soldering easy. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The addition of flux reduces surface tension of the molten tin. This helps it spread easily over the area of soldening. 

-Answered by Shruti Srivastva On 25 September 2020:06:22:36 PM


Question 19. Asked on :25 September 2020:06:18:07 PM

A tiny liquid drop is spherical but a larger drop has oval shape. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
In the caseof a tiny drop, the force of surface tension is large compared to its weight, so the drop has spherical shape. A large drop has oval shape because the force o gravity exceeds the force of surface tension. 

-Answered by Shruti Srivastva On 25 September 2020:06:19:20 PM


Question 20. Asked on :25 September 2020:06:15:11 PM

Glass marbles are made by heatig the end of a glass rod until drops of molten glass all. Explain.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When drops of molten glass fall freely, they are is state of weightlesness. As only the force of surace tension acts on them, so they acquire spherical shape which on solidififcation become glass marbles. 

-Answered by Shruti Srivastva On 25 September 2020:06:16:23 PM


Question 21. Asked on :25 September 2020:06:14:05 PM

A oil drop on a hot cup of soup spreads over when the temperature of the soup alls. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

nisha sheikh
The surface tension of oil is more than that of hor soup. Due to it, an oil drop does not spread over the hot soup. When the temperature of the soup falls, the surface tension of oil becomes less than that of soup. Due to it, the oil drop starts spreading on the soup.

-Answered by nisha sheikh On 21 October 2020:06:53:13 PM


Question 22. Asked on :25 September 2020:06:11:09 PM

How does soap help us to remove dirt better in washing clothes?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Wit the addition of soap, the surface tension of water decreaces. The decreaces in surace tension results in greater wetting and hence washing powder.  

-Answered by Shruti Srivastva On 25 September 2020:06:12:20 PM


Question 23. Asked on :25 September 2020:06:06:57 PM

The clothes are better cleaned with hot water than with cold watyer. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Surface tension decreaces with the increase of temperature. Lesser the surface tension, more is the wetting power of water. 

-Answered by Shruti Srivastva On 25 September 2020:06:09:48 PM


Question 24. Asked on :25 September 2020:05:59:18 PM

Why it becomes easier to spray the surace tension of water in which some soap is dissolved?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

 When soaps is dissolved in water, the surace tension of water decreaces and so less energy is neede for spraying the wateri.e., spraying of water in which soap is dissolved becomes is easier. 

-Answered by Shruti Srivastva On 25 September 2020:06:03:17 PM


Question 25. Asked on :25 September 2020:05:56:06 PM

A needle floats on the surface of pure water but goes down when detergent is added to water. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Due to addition of detergent, the surface tension and hence the reaction of surface tension decreaces. Hneca the needle sinks due to smaller upward reaction. 

-Answered by Shruti Srivastva On 25 September 2020:05:57:17 PM


Question 26. Asked on :25 September 2020:05:53:24 PM

Why do the hair of a shaving brush cling together when taking out of water? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When the brush is taken out of water, thin water film is formed at the tips of the hair. It contracts due to surface tension and so the hair cling together. 

-Answered by Shruti Srivastva On 25 September 2020:05:54:30 PM


Question 27. Asked on :25 September 2020:05:49:58 PM

Why does a stream of water from a fascet become narrow as it falls?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
This is due to surface tension. The molecule of water come close to each other due to surface tension and surface area tends to be minimum making the stream narrow. 

-Answered by Shruti Srivastva On 25 September 2020:05:50:53 PM


Question 28. Asked on :25 September 2020:05:48:27 PM

Why hot soup tastes better than cold soup? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Hot soups has compartevily less surface tension than cold soup.

-Answered by Shruti Srivastva On 25 September 2020:05:49:13 PM


Question 29. Asked on :25 September 2020:05:46:31 PM

Antiseptics have low surface tension. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Low surface tension helps the antiseptic to spread over large area over the wounds.

-Answered by Shruti Srivastva On 25 September 2020:05:47:36 PM


Question 30. Asked on :25 September 2020:05:42:23 PM

Why ends o a glass tube become rounded on heating? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When glass is heated, it melts to a liquid. The surface of this liqid tends to have a minimum area. Now , for a given volume, the area of the surface of a sphere is minimum. This is why the ends o a glass tube become rounded heating. 

-Answered by Shruti Srivastva On 25 September 2020:05:43:16 PM


Question 31. Asked on :25 September 2020:05:39:36 PM

Small insects can move about on the surface of water. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Due to surface tension, the free surface of water behaves like strecthed elastic membrane which is able to support the small weight of insects and they can move on the surface of water. 

-Answered by Shruti Srivastva On 25 September 2020:05:40:48 PM


Question 32. Asked on :25 September 2020:05:36:45 PM

One can from a fairly large vertical film a soap solution but not of pure water. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
This is because the surface tension o soap solution ismuch smaller than that of pure water. When we try to make a vertical film of pure water, it breaks due to the high surace tension of water.  

-Answered by Shruti Srivastva On 25 September 2020:05:37:48 PM


Question 33. Asked on :25 September 2020:05:35:57 PM

 Why shape does a liquid take when it weighs nothing? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Rohit Rajput
When a liquid weighs nothing, surface tension is the only force acting on it. Due to surface tension, the liquid surface tends to occupy minimum surface area. For a given volume, the surface area of a sphere is minimum, so the liquid assumes spherical shape.

-Answered by Rohit Rajput On 26 September 2020:07:21:43 PM


Question 34. Asked on :25 September 2020:05:35:18 PM

How dental plate clinges to the roof of the mouth? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Anjali Kumari
Dental plate clings to the roof of the mouth because of the presence of adhesive force between saliva and dental plate. 

-Answered by Anjali Kumari On 11 October 2020:02:09:13 PM


Question 35. Asked on :25 September 2020:05:33:24 PM

Why does mercury collect itsel into drops when placed on a clean glass plate? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The adhensive force between mercury and glass molecules is less than the cohensive force between mercury molecule. 

-Answered by Shruti Srivastva On 25 September 2020:05:34:19 PM


Question 36. Asked on :25 September 2020:05:29:55 PM

Why does the free surface of a liquid behave like an elastic steched membrane? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The liquid molecules on the surface experince a downward force. So they have greater potential energy. In order to minimum energy, the ree surface tends to contact to minimum area and hence behaves like an elastic steched membrane. 

-Answered by Shruti Srivastva On 25 September 2020:05:31:05 PM


Question 37. Asked on :25 September 2020:05:26:10 PM

Why is it not possible to seprate two piece of paper joined by glue or gum? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The adhesive force between the molecules of glue and paper is much more than the cohensive force between the glue molecules. As a result, the two papers stick together with a large force and cannot be seprated. 

-Answered by Shruti Srivastva On 25 September 2020:05:27:10 PM


Question 38. Asked on :25 September 2020:05:24:01 PM

Mercury doesn't cling to glass. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The force of adhension between mercury and glass is smaller than the force of cohension between the mercury molecules.

-Answered by Shruti Srivastva On 25 September 2020:05:24:37 PM


Question 39. Asked on :25 September 2020:05:21:00 PM

Why a glass rod caoted with wax does not become wet when dipped in water? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The reason is that force of adhension between water and wax molecules is smaller than force of cohension between water molecule.

-Answered by Shruti Srivastva On 25 September 2020:05:22:14 PM


Question 40. Asked on :24 September 2020:06:29:27 PM

Why are the cars and aeroplane gives streamline shape? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
To minimize the backward drag of atmosphere. 

-Answered by Shruti Srivastva On 24 September 2020:06:30:29 PM


Question 41. Asked on :24 September 2020:06:27:06 PM

Why bullets are given cylendrical shape? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The magnus effect is absent if the spinning cylinder is koving linearly in the direction parallel to spin axis. 

-Answered by Shruti Srivastva On 24 September 2020:06:28:18 PM


Question 42. Asked on :24 September 2020:06:23:31 PM

 An aeroplane runs for some distance on the runway before taking off. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Generally, air does not strike an aeroplane with a large velocity. To get lift, the aeroplane ruins for some distance on the runway before taking off.

-Answered by Shruti Srivastva On 24 September 2020:06:25:07 PM


Question 43. Asked on :24 September 2020:06:19:37 PM

When air is blown between two balls suspended close to each other, they are attached towards each other. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When air is blown between the two balls, the velocity is increased and hence pressure is decreased . On the outer sides of the balls, the pressure is high and hence the two balls get attached. 

-Answered by Shruti Srivastva On 24 September 2020:06:21:21 PM


Question 44. Asked on :24 September 2020:06:15:51 PM

Poofes of the huts are blown up during stormy days. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The velocity of the wind in high above the roof. So the pressure is low in accordance with Bernouilli's principle. But the pressure below the roof is the atmosphere pressure which is hogh. So the roof is blown up. 

-Answered by Shruti Srivastva On 24 September 2020:06:17:11 PM


Question 45. Asked on :24 September 2020:06:13:03 PM

Why does a flag flutter, when strong winds are blowing on a certain day?

-Added by Shruti Srivastva Physical Education » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When strong winds blow over the top of the flag, the kinetic energy o te wid at the top is more and hence pressure decreaces. Due to difference in pressure above and below the flag, the flag flutters. 

-Answered by Shruti Srivastva On 24 September 2020:06:14:00 PM


Question 46. Asked on :24 September 2020:06:10:16 PM

Why still water runs deep?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
In case of a deep water, the cross-sectional area, through which it flows, is quite large. Hence according to equation of continuity, its velocity is small and therefore it appears to be still. 

-Answered by Shruti Srivastva On 24 September 2020:06:10:52 PM


Question 47. Asked on :24 September 2020:06:08:02 PM

What happens to the external energy maintaining the flow of a liquid when the flow becomes turbulent? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The turbulent flow of a liquid, most of the external energy maintaining the flow is used in setting up the eddies in the liquid.

-Answered by Shruti Srivastva On 24 September 2020:06:09:11 PM


Question 48. Asked on :24 September 2020:06:04:51 PM

What happens when the velocity of a liquid becomes greater than its critical velocity? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The flow of liquid changes from streamline to turbulent. 

-Answered by Shruti Srivastva On 24 September 2020:06:07:01 PM


Question 49. Asked on :24 September 2020:06:02:42 PM

Why two stremline cannot cross each other ?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The two streamlines cross each other, there will be two directions of flow at the point o intersection which is possible.

-Answered by Shruti Srivastva On 24 September 2020:06:03:32 PM


Question 50. Asked on :24 September 2020:06:01:51 PM

The sides of a horizontal pipe carrying dirty water get dirty. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Rohit Rajput

 While flowing through the horizontal pipe, the velocity of dirty water is maximum along the axis of the pipe and minimum near the walls of the pipe. ... Due to this, the dirt particles move outwards and get struck on the walls of the pipe. This makes the pipe dirty.

-Answered by Rohit Rajput On 26 September 2020:07:16:36 PM


Question 51. Asked on :24 September 2020:06:00:26 PM

 Fog particles have very small sizes. So their terminal velocity through air is very small. They appear suspended in the atmosphere. 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Rohit Rajput
Fog particles are very tiny spheres. Since the terminal velocity through air of fog paticles is very small so the fog particles appears suspended in the atmosphere.

-Answered by Rohit Rajput On 26 September 2020:07:19:54 PM


Question 52. Asked on :24 September 2020:05:57:42 PM

Explain why parachute is invariably used, while jumping from an aeroplane? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
A parachute experience a large viscous force due its huge structure. Hence, it descends through the air with a very small velocity and the parachute desn't get hurt. 

-Answered by Shruti Srivastva On 24 September 2020:05:58:48 PM


Question 53. Asked on :24 September 2020:05:55:01 PM

Why dust generally settles down in a closed room? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Dust particle are speres of small radii. After accuring the terminal velocity they start falling through air with uniform speed. 

-Answered by Shruti Srivastva On 24 September 2020:05:55:48 PM


Question 54. Asked on :24 September 2020:05:52:43 PM

When rain drop falling under gravity do mot grain very high velocity? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Rohit Rajput

 Explanation:When a rain drop falls under gravity throght a viscous medium (say air) a viscous drag acts on it in a direction opposite to that of motion. ... At this stage, there is no net force to ac celerate rain drop. Hence the rain drop starts moving with uniform velocity .

-Answered by Rohit Rajput On 26 September 2020:07:17:38 PM


Question 55. Asked on :24 September 2020:05:40:33 PM

Why does an object rntering the earth's atnosphere at high velocity catch fire? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

 When an object enters the earth atmosphere at high velocity, its motion is strongly opposed by the viscous drag of air. 

-Answered by Shruti Srivastva On 24 September 2020:05:50:30 PM


Question 56. Asked on :24 September 2020:05:34:38 PM

Why should the lubricant oil be of high viscosity? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Lubricant oil is used to reduce the dry friction between various machine parts. Due to high viscosity, lubricant oils sticks to the machine parts and cannot be squeezed out during the working of the machine. 

-Answered by Shruti Srivastva On 24 September 2020:05:36:09 PM


Question 57. Asked on :24 September 2020:05:32:35 PM

Why machine parts are jammed in the winter? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

In winter the coefficient of viscosity of the lubricating ols gets increased due to fall in temperature. 

-Answered by Shruti Srivastva On 24 September 2020:05:33:35 PM


Question 58. Asked on :24 September 2020:05:30:04 PM

Why oils of different viscosity are used in different season? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Due to the rise of temperature in summer, the viscosity of oil decreaces. Hence more viscous oils are used in summer than winter. 

-Answered by Shruti Srivastva On 24 September 2020:05:31:09 PM


Question 59. Asked on :24 September 2020:05:26:45 PM

Hotter liquids move faster than cooler ones. why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

 The viscosity or the internal force of friction of a liquid decreaces with the increase in temperature. Hence hotter liquids move fastter than colder ones.

-Answered by Shruti Srivastva On 24 September 2020:05:27:34 PM


Question 60. Asked on :24 September 2020:05:24:54 PM

What is the efect of temperature on the viscocity and liquid and gases? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The viscocity of liquids decreaces with rise in temperature while that of gases increace with an increase in temperature. 

-Answered by Shruti Srivastva On 24 September 2020:05:25:46 PM


Question 61. Asked on :24 September 2020:05:20:26 PM

What is the reason that a constant driving force is always required for the maintainance of the flow of oil through the pipe lines in the oil refineries? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Due to viscous force between the layers of oil, the motion o liquids gets retaerded after a certain distnace. Hence a constant driving force is required for maintaining the flow of oil through the pipe line. 

-Answered by Shruti Srivastva On 24 September 2020:05:22:25 PM


Question 62. Asked on :24 September 2020:05:18:12 PM

 Stirred liquid comes to rest after some time. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Different layers of a stirred liquid distroy the relative motion among themselves due to internal viscous force.

-Answered by Shruti Srivastva On 24 September 2020:05:19:07 PM


Question 63. Asked on :23 September 2020:05:54:26 PM

A soft plastic bag weights the same when empty as when filled with air at atmospheric pressure. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The weight of air displced by the bag is same as the weight of air inside it. The increse in weight due to the filled air gets cancelled by the upthrust of air. So weight remains same when air is filled in the bag. 

-Answered by Shruti Srivastva On 23 September 2020:05:55:46 PM


Question 64. Asked on :23 September 2020:05:27:43 PM

Why a sinking ship often turns over as it becomes immersed in water? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When the ship is floating, the metra-centre of the ship is above the centre of gravity. While sinking, the ship takes in water. As a result, the centre of gravity is raised above the metra-centre. The ship turns over due to the couple formed by the weight and the buoyant orce. 

-Answered by Shruti Srivastva On 23 September 2020:05:29:00 PM


Question 65. Asked on :23 September 2020:05:24:43 PM

A wooden cylinder floats in a vessel with its axis vertical. How will the level of water in the vesel change if the cylinder floats with its axis horizontal? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The level of water will not chage because in both cases, the cylinder displaced equal volume of water. 

-Answered by Shruti Srivastva On 23 September 2020:05:26:33 PM


Question 66. Asked on :23 September 2020:05:21:30 PM

Why is it easier to swim in sea water then in river water? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The sea water has many salts dissolved into it. So, the density of sea water is greater than that of river water. Consequently, the sea water exerts greater upthrust on the swimmer than the river water. 

-Answered by Shruti Srivastva On 23 September 2020:05:22:51 PM


Question 67. Asked on :22 September 2020:06:00:20 PM

A piece of cork is floating in water contained a beaker. What is the apparent weight of the cork piece? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The weight of the cork piece acting vertically downwards is balanced by the upthrust due to water. So the apparent weight of the floating cork piece is zero. 

-Answered by Shruti Srivastva On 22 September 2020:06:01:55 PM


Question 68. Asked on :22 September 2020:05:59:00 PM

Does the Archimedes principle hold in a vessel in free fall? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

 no.

-Answered by Shruti Srivastva On 22 September 2020:06:00:07 PM


Question 69. Asked on :22 September 2020:05:57:13 PM

An ice cube floats in a glss of water illed to the brim. What happens when the ice melts?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The water level remains uncharged. 

-Answered by Shruti Srivastva On 22 September 2020:05:58:35 PM


Question 70. Asked on :22 September 2020:05:51:57 PM

A man is sitting in a boat, which is floating in a pond. If the man drinks some water from the pond, will the level of water in the pond fall? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

 Levels remain same. 

-Answered by Shruti Srivastva On 22 September 2020:05:56:53 PM


Question 71. Asked on :22 September 2020:05:49:07 PM

A piece of iron sinks in water, but a ship made of iron floats in water. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The weight of water displaced by iron piece is less than its own weight, so it sinks. On the other hand, tha ship displaces water more than its own weight, so it floats. 

-Answered by Shruti Srivastva On 22 September 2020:05:50:20 PM


Answer:

Shruti Srivastva
Since there is no water under the block to exert an upward orce on it, thereore, there is no buoyant force. 

-Answered by Shruti Srivastva On 22 September 2020:05:47:59 PM


Question 73. Asked on :22 September 2020:05:41:44 PM

A liquid cannot withstand a shear stress. How does this imply that the surface of a liquid at rest must be level, i.e., normal to the gravitational force? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
If the free surface of the liquid is not perpendicular to the gravitational force, then there will be a componenet of force along the surface. The liquid will not be at rest in that case.

-Answered by Shruti Srivastva On 22 September 2020:05:44:09 PM


Question 74. Asked on :22 September 2020:05:39:46 PM

Why does a siphon fail to work in vaccum? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
As siphon works on account of atmospheric pressure, hence it fails to work in vaccum. 

-Answered by Shruti Srivastva On 22 September 2020:05:40:34 PM


Question 75. Asked on :22 September 2020:05:38:37 PM

Why an air bubble in water rises form bottom to top and grow in size? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Rohit Rajput
As air bubble rises from bottom to the top of a water tank, the size of the bubble increases. It happens, because. the pressure exerted by water on the bubble decreases as the height of the water column above it decrease. the density of water increases as we move downwads.

-Answered by Rohit Rajput On 26 September 2020:07:18:29 PM


Question 76. Asked on :22 September 2020:05:35:27 PM

The dams of water reservoir are made thick near the bottom. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Pressure exerted by a liquid column of height. As the value of h is greatest near the bottom, so pressure exerted by water is greatest near the bottom. So dams are made thick near the bottom. 

-Answered by Shruti Srivastva On 22 September 2020:05:36:57 PM


Question 77. Asked on :22 September 2020:05:33:06 PM

How can we check whether the barometric tube contains air or not? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
If on raising or lowering the barometric tube in a trough of mercury, the height of mercury column changes, than air is present in the barometric tube. 

-Answered by Shruti Srivastva On 22 September 2020:05:34:03 PM


Question 78. Asked on :22 September 2020:05:29:53 PM

Why is raeding of a mercury barometer always less than actual pressure? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Due to property of surface tension, mercury in the tube gets depressed. Consequqntly, the observed height of mercury in the barometer tube is less than its actual height. Thus, the reading of mercury barometer is always less than the actula pressure. 

-Answered by Shruti Srivastva On 22 September 2020:05:30:46 PM


Question 79. Asked on :22 September 2020:05:28:14 PM

Why is mercury is used in barometer?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
(i) It does not stick on the wall.

(ii) Its vapour pressure quite small. 

-Answered by Shruti Srivastva On 22 September 2020:05:28:58 PM


Question 80. Asked on :22 September 2020:05:25:23 PM

Why water is not used in barometer?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

(i) It sticks to the walls of the barometer tube.

(ii) It has low density, A barometer with water will require a tube legth of about 11m which is unmanageable. 

-Answered by Shruti Srivastva On 22 September 2020:05:26:09 PM


Question 81. Asked on :22 September 2020:05:23:22 PM

If a drop of water vapour is introduced in a mercury barometer, how will the barometric height change? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Due to pressure exerted by water vapour, the barometric height decrases. 

-Answered by Shruti Srivastva On 22 September 2020:05:24:37 PM


Question 82. Asked on :22 September 2020:05:20:45 PM

Why are straw used to suck soft drink?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When we suck through the straw, the pressure inside the straw becomes less than the atmospheric pressure. Due to the pressure differences, the soft drink rises in the straw and we are able to takle the soft drink. 

-Answered by Shruti Srivastva On 22 September 2020:05:21:34 PM


Question 83. Asked on :22 September 2020:05:18:12 PM

Why is it dificult to stop bleeding rom a cut in a human body at high altitudes? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The atmospheric pressure is low at high altitudes. Due to greater pressure difference in blood pressure and the atmospheric pressure, it is diicult to stop bleeding from a cut in a body. 

-Answered by Shruti Srivastva On 22 September 2020:05:19:17 PM


Question 84. Asked on :22 September 2020:05:14:42 PM

Why the passengers are advised to remove the ink from their pens while going up in an aeroplane? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
We know that the atmospheric pressure decreaces with hsight. Since ink inside the pen is filled at the atmospheric pressure exsisting n surace of the earth, it tends to come out to equalise the pressure. This can spoil the clothes of the passengers, so they are advised to rmove the ink from the pen. 

-Answered by Shruti Srivastva On 22 September 2020:05:15:44 PM


Question 85. Asked on :21 September 2020:06:22:44 PM

Why the ood is cooked faster in the pressure cooker? Why it becomes difficult to cook food at the mountains? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The pressure inside the pressure cooker is very high. The raises the boiling point of water and the temperature inside the cooker is higher than 100ºC which results in faster cooking the food. 

-Answered by Shruti Srivastva On 21 September 2020:06:24:02 PM


Question 86. Asked on :21 September 2020:06:19:48 PM

Why the boiling point of a liquid varues with pressure? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
At the boiling point, vapour pressure of the liquid is equal to the atmosheric pressure on the surface of the liquid increaces the liquid boils at higher temperature to generate greater vapour pressure. 

-Answered by Shruti Srivastva On 21 September 2020:06:20:53 PM


Question 87. Asked on :21 September 2020:06:16:23 PM

How does the boling point of liquid vary with pressure? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The boling point o a liquid increases with the pressure, or example, if the pressure is more thanthe atmospheric pressure, water bolis at a temperature higher than 100ºC.

-Answered by Shruti Srivastva On 21 September 2020:06:17:48 PM


Question 88. Asked on :21 September 2020:06:08:43 PM

What is the force on a man due to atmospheric pressure? Why on does not feel it? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Atmospheric pressure on the eaath is about 1 kg f per square centimetre. The surface area of the body of average man is about 2m2 and hence, a total force equal to about 2 × 105 N, acts on the body of a man due to atmospheric pressure =. But one does not eel this enormous orce because his blood exert a pressured slightly greater than the atmospheric pressure. 

-Answered by Shruti Srivastva On 21 September 2020:06:11:30 PM


Question 89. Asked on :21 September 2020:05:59:11 PM

Why is a slight blow on a cork of a bottle filled with a liquid suicient to break the bottle? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The blow on the cork exerts a pressure ( = f /a) on the liquid. Acccording to the pascal's law, this pressure is transmitted to the entire bottle through the liquid. Since the surace are (A) of the bottle is large, the large force ( = fA/u) so developed is sufficient to break the bottle. 

-Answered by Shruti Srivastva On 21 September 2020:06:04:03 PM


Question 90. Asked on :21 September 2020:05:56:47 PM

Why two holes are made to empty an oil tin?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When two holes are made in the tin, air keeps on entering the tim through the other hole and maintains pressure inside. 

-Answered by Shruti Srivastva On 21 September 2020:05:58:00 PM


Question 91. Asked on :21 September 2020:05:53:39 PM

Water does not come out of a dropper unless its rubber bulb is pressed hard. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Water is heild inside the dropper against the atmospheric pressure. When the rubber bulb is pressed, pressure on water becomes greter than the atmospheric pressure and so water comes out. 

-Answered by Shruti Srivastva On 21 September 2020:05:54:55 PM


Question 92. Asked on :21 September 2020:05:50:57 PM

It is difficult for a man to walk on sand. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
This is because sand yeild under the weight of the man. This difficulty can be overcome by placing wooden plack on the sand. 

-Answered by Shruti Srivastva On 21 September 2020:05:52:16 PM


Question 93. Asked on :21 September 2020:05:47:37 PM

It is painful to walk barefooted on the groung covered with the edged pebbles. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
When walking, when entire weight of our body gets supported on the sharp edge of any pebble, it will exert a large pressue on our feet due to reaction. This causes considerable pain on our feet. 

-Answered by Shruti Srivastva On 21 September 2020:05:48:54 PM


Question 94. Asked on :21 September 2020:05:43:49 PM

Railway tracks are laid on the large sized wooden sleepers. Why? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The spread force due to the wieght of the train on a large area and hence reduced the pressure considerably. This, In turn, prevents yeilding of the ground under the weight of the train. 

-Answered by Shruti Srivastva On 21 September 2020:05:44:55 PM


Question 95. Asked on :21 September 2020:05:41:14 PM

Whay are the bags and suitcases provided with broad handles?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Broad handles have large area. So the force per unit area or the pressure exerted on the hand will be small while carrying the bag or the suitcase.

-Answered by Shruti Srivastva On 21 September 2020:05:42:22 PM


Question 96. Asked on :21 September 2020:05:36:06 PM

We can cut an apple easily with a sharp knife as compared to withe a blunt knife. Why?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
Because the area of sharp knife is lesser than a blunt knife.

-Answered by Shruti Srivastva On 21 September 2020:05:40:40 PM


Question 97. Asked on :27 July 2020:06:10:37 PM

Give relationship between poise and decapoise. 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

 1 Decapoise = 10 poise .

-Answered by Shruti Srivastva On 27 July 2020:06:11:37 PM


Question 98. Asked on :27 July 2020:06:09:01 PM

By which phenomenon, the water rises fro roots to leaves of plants?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The water rises fro roots to leaves of plants by Capillary action.

-Answered by Shruti Srivastva On 27 July 2020:06:09:59 PM


Answer:

Shruti Srivastva

The terminal of second sphere will be 9 v because v1 ∝ r2


-Answered by Shruti Srivastva On 27 July 2020:06:07:17 PM


Question 100. Asked on :27 July 2020:06:03:15 PM

Name the material in whose capillary water will descend instead of rising. 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The material in whose capillary water will descend instead of rising is paraffin wax. 

-Answered by Shruti Srivastva On 27 July 2020:06:04:13 PM


Question 101. Asked on :27 July 2020:06:01:40 PM

What is capillarity?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The phenomenon of rise or fell of a liquid in a capillary with respect to the surrounding is called capillarity. 

-Answered by Shruti Srivastva On 27 July 2020:06:02:10 PM


Question 102. Asked on :27 July 2020:05:59:35 PM

What happens to the surface tension when some impurity is mixed in liquid?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

If the liquid surface has dust, grease or oil, the surface tension of liquid decreases. 

-Answered by Shruti Srivastva On 27 July 2020:06:00:46 PM


Question 103. Asked on :27 July 2020:05:55:59 PM

What are the factors on which the angle of contacts depends?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

(i) Nature of the solid and liquid in contact.

(ii) Cleanliness of the surface in contact.

(iii) Medium above the free surface of the liquid.

(iv) Temperature of the liquid.

-Answered by Shruti Srivastva On 27 July 2020:05:57:33 PM


Question 104. Asked on :27 July 2020:05:54:26 PM

Will the angle of contact be acute or obtuse for liquids which do not wet the walls of the container?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Obtuse                       .

-Answered by Shruti Srivastva On 27 July 2020:05:57:09 PM


Question 105. Asked on :27 July 2020:05:52:15 PM

Will the angle of contact be acute or obtuse for liquids which wet the walls of the container?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Acute                                                                       .

-Answered by Shruti Srivastva On 27 July 2020:05:53:46 PM


Question 106. Asked on :27 July 2020:05:49:44 PM

What is the effect of solute on the surface tension of a liquid?

-Added by Shruti Srivastva Physical Education » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Angle of contact is defined as the angle between the tangent to the liquid surface at the point of contact to the solid inside the liquid. 

-Answered by Shruti Srivastva On 27 July 2020:05:50:52 PM


Question 107. Asked on :27 July 2020:05:48:22 PM

What is the value of surface tension at the critical temperature? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The value of surface tension at the critical temperature is zero.

-Answered by Shruti Srivastva On 27 July 2020:05:49:14 PM


Question 108. Asked on :27 July 2020:05:46:18 PM

Write down the following liquids in the order of increasing surface tension: 

            Water, mercury, soap solution.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
soap solution, Water, mercury.

-Answered by Shruti Srivastva On 27 July 2020:05:47:53 PM


Question 109. Asked on :27 July 2020:05:44:41 PM

How does surface tension change with temperature ?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The surface tension of a liquid decreases with the rise of temperature.

-Answered by Shruti Srivastva On 27 July 2020:05:45:37 PM


Question 110. Asked on :27 July 2020:05:42:31 PM

Which part of the liquid is responsible for the phenomenon of surface tension?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The liquid in surface film is responsible for surface tension.

-Answered by Shruti Srivastva On 27 July 2020:05:43:45 PM


Question 111. Asked on :27 July 2020:05:40:23 PM

Define sphere of influence of a liquid molecule .

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

A sphere drawn around a molecule as center and radius equal to the molecular range is called the sphere of influence of a liquid molecule .

-Answered by Shruti Srivastva On 27 July 2020:05:41:23 PM


Question 112. Asked on :27 July 2020:05:36:33 PM

What is meant by the term molecular range?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

 The maximum distance up to which a molecule can exert measurable force of attraction on other molecules is called molecular range (=10-9m). 

-Answered by Shruti Srivastva On 27 July 2020:05:37:35 PM


Question 113. Asked on :27 July 2020:05:34:26 PM

Name a physical quantity that has same dimensions as surface tension.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The physical quantity that has same dimensions as surface tension is spring constant.

-Answered by Shruti Srivastva On 27 July 2020:05:35:51 PM


Question 114. Asked on :27 July 2020:05:30:05 PM

State SI unit of surface tension. 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

SI unit of surface tension is Nm-1 

-Answered by Shruti Srivastva On 27 July 2020:05:32:22 PM


Question 115. Asked on :27 July 2020:05:26:31 PM

Define surface tension.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The property of a liquid by virtue of which its free surface at rest behaves like a stretched membrane and tends to have the minimum surface area is called surface tension   

-Answered by Shruti Srivastva On 27 July 2020:05:27:03 PM


Question 116. Asked on :27 July 2020:05:24:12 PM

Define force of cohesion?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The force of attraction between the molecules of the same substance is called the force of cohension.

-Answered by Shruti Srivastva On 27 July 2020:05:24:44 PM


Question 117. Asked on :27 July 2020:05:22:55 PM

State the principle on which pitot tube based?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

It is based on Bernoulli's theorem.

-Answered by Shruti Srivastva On 27 July 2020:05:23:34 PM


Question 118. Asked on :27 July 2020:05:18:43 PM

What is a Pitot tube?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

It is a device which is used to measure the velocity of the flows at any depth in a flowing liquid. 

-Answered by Shruti Srivastva On 27 July 2020:05:20:03 PM


Question 119. Asked on :27 July 2020:05:17:38 PM

State Bernoulli's theorem.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Refer to point 36 of Glimpses.

-Answered by Shruti Srivastva On 27 July 2020:05:18:20 PM


Question 120. Asked on :27 July 2020:05:14:44 PM

State Torricelli's theorem.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Torricelli's theorem states that the velocity with which a liquid flows out through an orifice at a certain depth below the free surface is the same as that attained by another body which falls freely through the same height.  

-Answered by Shruti Srivastva On 27 July 2020:05:15:23 PM


Question 121. Asked on :27 July 2020:05:11:37 PM

What should be the properties of a liquid ton satisfy Bernoulli's theorem?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The liquid should be incompressible and non-viscous and flow of the liquid should be streamlined and irrotational.

-Answered by Shruti Srivastva On 27 July 2020:05:12:52 PM


Question 122. Asked on :27 July 2020:01:47:15 PM

Write the expressions for pressure head, gravitational head and velocity head?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva


Pressure head = PPG ,

Gravitational head = h and velocity head = v22g 

-Answered by Shruti Srivastva On 27 July 2020:01:48:44 PM


Question 123. Asked on :27 July 2020:01:45:13 PM

What is that fundamental principle on which Bernoulli's theorem is based?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Law of conversation of energy.

-Answered by Shruti Srivastva On 27 July 2020:01:46:42 PM


Question 124. Asked on :27 July 2020:01:42:36 PM

What is an ideal fluid?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

An ideal fluid is one which is non-viscous, in compressible and its flow is steady and irrational.

-Answered by Shruti Srivastva On 27 July 2020:01:43:21 PM


Question 125. Asked on :27 July 2020:01:40:07 PM

What are the different forms of energy possessed by a fluid in a streamline flow?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

(i) Kinetic energy, (ii) Potential energy and (ii) Pressure energy.

-Answered by Shruti Srivastva On 27 July 2020:01:41:33 PM


Question 126. Asked on :27 July 2020:01:36:07 PM

What will be the nature of graph between the velocity of fluid flow (v) and area of cross section (a) of the pipe?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The nature of graph between the velocity of fluid flow (v) and area of cross section (a) of the pipe is Rectangular hyperbola.





-Answered by Shruti Srivastva On 27 July 2020:01:38:25 PM


Question 127. Asked on :27 July 2020:01:33:43 PM

What is fundamental law forms the basis of equation of continuity?  

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Law of conversation of mass.

-Answered by Shruti Srivastva On 27 July 2020:01:35:38 PM


Question 128. Asked on :27 July 2020:01:31:21 PM

What is critical velocity of a liquid?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Critical velocity is the maximum velocity of liquid above which the flow of a liquid changes from streamline to turbulent.

-Answered by Shruti Srivastva On 27 July 2020:01:32:08 PM


Question 129. Asked on :27 July 2020:01:28:35 PM

Write the true value of Reynolds's number for turbulent flow?

-Added by Shruti Srivastva Physical Education » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The true value of Reynolds's number for turbulent flow is 3000.




-Answered by Shruti Srivastva On 27 July 2020:01:30:23 PM


Question 130. Asked on :27 July 2020:01:22:10 PM

Write the dimensional formula of Reynolds number?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

T he dimensional formula of Reynolds number is [M0L0T0]

-Answered by Shruti Srivastva On 27 July 2020:01:27:29 PM


Question 131. Asked on :27 July 2020:01:17:57 PM

What is the range of Reynolds's number for the laminar flow of a liquid?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

For laminar flow, Re lies between 0 and 2000.

-Answered by Shruti Srivastva On 27 July 2020:01:20:17 PM


Question 132. Asked on :27 July 2020:01:15:36 PM

What is Reynolds's number?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Reynolds's number is dimensionless combination of four factors which decides the nature of flow a vicious liquid through a pipe.

-Answered by Shruti Srivastva On 27 July 2020:01:16:23 PM


Question 133. Asked on :27 July 2020:01:13:16 PM

What is laminar flow of a liquid?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The type of flow of a liquid in which its layers slide over one another without mixing is called the laminar flow.

-Answered by Shruti Srivastva On 27 July 2020:01:14:06 PM


Question 134. Asked on :27 July 2020:01:10:49 PM

When does the streamline flow become turbulent? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The streamline flow become turbulent flow when the velocity of the liquid exceeds the critical velocity.

-Answered by Shruti Srivastva On 27 July 2020:01:11:48 PM


Question 135. Asked on :27 July 2020:01:06:40 PM

What do mean by a streamline and a tube of flow?

-Added by Shruti Srivastva Physical Education » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

A streamline may be defined as the straight or curved path, such that the tangent to it at any point gives the direction of flow of the liquid at the point. A group of of streamlines is said to form a tube of flow.

-Answered by Shruti Srivastva On 27 July 2020:01:07:44 PM


Question 136. Asked on :27 July 2020:01:02:55 PM

What is the net weight of a body when it falls with terminal velocity through a viscous medium?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Zero, because the weight of the body acting vertically downwards is balanced by the viscous force and the upthrust due to the medium.

-Answered by Shruti Srivastva On 27 July 2020:01:04:29 PM


Question 137. Asked on :27 July 2020:12:59:13 PM

Two balls A and B have radii in the ratio 1:2. What will be the ratio of their terminal velocities in a liquid?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

As v ∝ r2 , so the ratio of the terminal velocities of A and B will be 4:1.

-Answered by Shruti Srivastva On 27 July 2020:01:01:03 PM


Question 138. Asked on :27 July 2020:12:56:52 PM

What is the nature of graph between terminal velocity of a spherical body and the square of its radius?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Straight line is the nature of graph between terminal velocity of a spherical body and the square of its radius.

-Answered by Shruti Srivastva On 27 July 2020:12:58:29 PM


Question 139. Asked on :27 July 2020:12:54:29 PM

Out os solid friction and viscous force, which is independent of velocity?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Solid friction is independent of velocity.

-Answered by Shruti Srivastva On 27 July 2020:12:56:12 PM


Question 140. Asked on :27 July 2020:12:51:47 PM

Mention two applications of stoke's law.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Stroke's law can be used to find (i) Radius of a drop of oil (ii) coefficient of viscosity of a liquid.

-Answered by Shruti Srivastva On 27 July 2020:12:52:48 PM


Question 141. Asked on :27 July 2020:12:48:29 PM

State stoke's law?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

According to stoke's law the viscous drag on a small body of radius moving with a uniform velocity through a viscous medium of viscosity is given by    F = 6π n rv.

-Answered by Shruti Srivastva On 27 July 2020:12:49:03 PM


Question 142. Asked on :27 July 2020:12:46:09 PM

Water flows through a pipe. Which of its layers moves fastest?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The axial layer of water moves fastest.

-Answered by Shruti Srivastva On 27 July 2020:12:47:33 PM


Question 143. Asked on :27 July 2020:12:43:09 PM

How does the viscosity of gas depend on temperature? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The viscosity of the gases increases with the increase of tempreature. For a gas, n ∝ √T

-Answered by Shruti Srivastva On 27 July 2020:12:44:20 PM


Question 144. Asked on :27 July 2020:12:40:10 PM

Define kinematic viscosity. 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The ratio of coefficient of viscosity n and the density p of a liquid is called its kinetic viscosity.

-Answered by Shruti Srivastva On 27 July 2020:12:41:16 PM


Question 145. Asked on :27 July 2020:12:36:41 PM

Define decapoise.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The coefficient of viscosity of a liquid is said to be 1 decapitate if tangential force of 1 Nm-2of the surface is required to maintain a relative velocity of 1 ms-1 between two layers of the liquid 1 m apart. 

-Answered by Shruti Srivastva On 27 July 2020:12:37:20 PM


Question 146. Asked on :27 July 2020:12:32:56 PM

Define poise.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The coefficient of viscosity of a liquid is said to be 1 poise if a tangential force of 1 dyne cm-2 of the surface is required to maintain a relative velocity of 1 cms-1between two layers of the liquid 1 cm a part.

-Answered by Shruti Srivastva On 27 July 2020:12:33:30 PM


Question 147. Asked on :27 July 2020:12:29:33 PM

State the dimensional formula of the coefficient of viscosity.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The dimensional formula of the coefficient of viscosity is [ML-1T-1].

-Answered by Shruti Srivastva On 27 July 2020:12:30:52 PM


Question 148. Asked on :27 July 2020:12:27:21 PM

Name the CGS and SI unit of the coefficient of viscosity?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
The CGS unit of the coefficient of viscosity is poise and SI unit of the coefficient of viscosity is decapoise.

-Answered by Shruti Srivastva On 27 July 2020:12:28:28 PM


Question 149. Asked on :27 July 2020:12:24:40 PM

Define the coefficient of viscosity of a liquid.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The coefficient of viscosity of liquid is defined as the tangential viscous force required to maintain a unit velocity gradient between liquid layers each of unit area.

-Answered by Shruti Srivastva On 27 July 2020:12:25:38 PM


Question 150. Asked on :27 July 2020:12:23:20 PM

What is reciprocal of viscosity known as ?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The reciprocal of viscosity known as Fluidity.

-Answered by Shruti Srivastva On 27 July 2020:12:24:09 PM


Question 151. Asked on :27 July 2020:12:20:31 PM

Define Viscosity. 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Viscosity is the property of the fluid by virtue of which it opposes the relative lotion between its different layers.

-Answered by Shruti Srivastva On 27 July 2020:12:21:17 PM


Question 152. Asked on :27 July 2020:12:18:41 PM

What is the internal force of friction of a fluid known as ?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The internal force of friction of a fluid known as Viscosity.

-Answered by Shruti Srivastva On 27 July 2020:12:19:42 PM


Question 153. Asked on :27 July 2020:12:15:07 PM

I n case of stable equilibrium, should the meta-center be above or below the center of gravity of the body?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Meta-center should be above the center of gravity.

-Answered by Shruti Srivastva On 27 July 2020:12:16:56 PM


Question 154. Asked on :21 July 2020:06:16:17 PM

How much should be diasolic blood pressure of a normal human being? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Nearly 80 mm of Hg . 

-Answered by Shruti Srivastva On 21 July 2020:06:17:37 PM


Question 155. Asked on :21 July 2020:06:14:50 PM

How much should be sytolic blood pressure for a normal human being?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Nearly 120 mm of Hg .

-Answered by Shruti Srivastva On 21 July 2020:06:15:49 PM


Question 156. Asked on :21 July 2020:06:13:23 PM

In which case a body will weigh maximum?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

In vaccum body will weigh maximum.

-Answered by Shruti Srivastva On 21 July 2020:06:14:06 PM


Question 157. Asked on :21 July 2020:06:11:48 PM

Define buoyancy.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

When a body is immersed in a fluid, it experiences a thrust. This effect is called buoyancy.

-Answered by Shruti Srivastva On 21 July 2020:06:12:21 PM


Question 158. Asked on :21 July 2020:06:08:03 PM

What will happen if water is used in place of mercury in a barometric tube?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

If water is ysed as barometric substance, it would require a tube about 11m long. It is difficult to hold such a type in a vertical position.

-Answered by Shruti Srivastva On 21 July 2020:06:10:10 PM


Question 159. Asked on :21 July 2020:06:04:59 PM

 What prctical unit of pressure is used in meteorological science?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Atmospheric pressure (atm)

1 atm = 1.013 x 10Nm-2.

-Answered by Shruti Srivastva On 21 July 2020:06:06:20 PM


Question 160. Asked on :21 July 2020:06:03:20 PM

What is indicated by gradual increase of atmospheric pressure? 

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

It Indicates dry weather .

-Answered by Shruti Srivastva On 21 July 2020:06:04:19 PM


Question 161. Asked on :21 July 2020:05:56:29 PM

What does sudden fall in barometric height indicate?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

It indicate possibility of storm.

-Answered by Shruti Srivastva On 21 July 2020:06:02:52 PM


Question 162. Asked on :21 July 2020:05:49:37 PM

If water is used instead of mercury in a barometer, what will be the height of water column?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The height of water column will be 10.34.

-Answered by Shruti Srivastva On 21 July 2020:05:51:01 PM


Question 163. Asked on :21 July 2020:05:47:48 PM

What is manometer?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Manometer is a device used to measure the pressure of a gas enclosed in a vessel.

-Answered by Shruti Srivastva On 21 July 2020:05:48:34 PM


Question 164. Asked on :21 July 2020:05:41:54 PM

Name the scientist who first experimentally measured the atmospheric pressure.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Torricellie is the scientist who first experimentally measured the atmospheric pressure.

-Answered by Shruti Srivastva On 21 July 2020:05:43:25 PM


Question 165. Asked on :21 July 2020:05:38:41 PM

Name the factors on which the atmosphere pressure at a place depends.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

(i) Height of atmosphere

(ii) Density of atmosphere  

(iii) Acceleration due to gravity.

-Answered by Shruti Srivastva On 21 July 2020:05:40:14 PM


Question 166. Asked on :21 July 2020:05:33:24 PM

Write the relation between torr and millibar?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

1 torr = 133.8 Nm-2 = 133.8 105 bar = 1.338 millibar . 

 

-Answered by Shruti Srivastva On 21 July 2020:05:34:46 PM


Question 167. Asked on :21 July 2020:05:31:40 PM

What is meant by one bar of pressure?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

 1 bar = 105 Nm-2 . 

-Answered by Shruti Srivastva On 21 July 2020:05:32:30 PM


Question 168. Asked on :21 July 2020:05:28:47 PM

What is one torr of pressure?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

1 Torr = pressure exerted by 1 mm Hg column =10-3 x 13.6 x 103 x 9.8 = 133.8 Nm-2.

-Answered by Shruti Srivastva On 21 July 2020:05:29:29 PM


Question 169. Asked on :21 July 2020:05:25:55 PM

Does the atmospheric pressure vary with the height above the earth's surface?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

The atmospheric pressure decreaces with the height above the earth's surface.

-Answered by Shruti Srivastva On 21 July 2020:05:27:42 PM


Question 170. Asked on :21 July 2020:05:23:00 PM

What is atmospheric pressure?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Atmospheric pressure at any point is equal to weight of air contained in a column of unit cross-sectional area and extending up to top of atmosphere.

-Answered by Shruti Srivastva On 21 July 2020:05:23:51 PM


Question 171. Asked on :21 July 2020:05:20:42 PM

Name two practical applications of Pascal's law?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Hydraulic press hydraulic breakes.

-Answered by Shruti Srivastva On 21 July 2020:05:21:54 PM


Question 172. Asked on :21 July 2020:05:17:38 PM

State Pascal's Law .

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Pascal's law states that a change in pressure applied to an enclosed incompressible fluid is transmitted undiminished to every point of the fluid an the walls of the containing vessels. 

-Answered by Shruti Srivastva On 21 July 2020:05:18:29 PM


Question 173. Asked on :21 July 2020:05:16:05 PM

Is thrust is a vector or a scalar quantity?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Thrust is a vector quantity.

-Answered by Shruti Srivastva On 21 July 2020:05:16:57 PM


Question 174. Asked on :21 July 2020:05:14:39 PM

 What is the modulus rigidity of fluid?

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva

Zero, A fluid has no definite shape of its own.

-Answered by Shruti Srivastva On 21 July 2020:05:15:24 PM


Question 175. Asked on :21 July 2020:05:11:28 PM

Define the term fluid.

-Added by Shruti Srivastva Physics » Mechanical Properties Of Fluids

Answer:

Shruti Srivastva
A fuluid is a substance that flows. So the term fluid refers to both liquid and gases.

-Answered by Shruti Srivastva On 21 July 2020:05:13:10 PM


 

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