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Asked/Added Questions From NCERT:


Question 1. Asked on :14 July 2020:01:48:03 PM

 What is the work done by centripetal force in moving a body through half cycle on the circular path of radius 35m?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Zero, because centripetal force  direction on motion.

-Answered by Shruti Srivastva On 14 July 2020:01:49:53 PM


Question 2. Asked on :14 July 2020:01:40:51 PM

 How does the kinetic energy of a moving ball change if its speed is reduced to half of original speed. Take mass of ball = 4 kg and original speed = 20m/s.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 K= ½ X 4 X 20 = 800 J

Kf = ½ x 4 x 102 =200j

Decrease in K.E. = 800 - 200 = 600 j.

-Answered by Shruti Srivastva On 14 July 2020:01:43:09 PM


Question 3. Asked on :14 July 2020:01:37:37 PM

 How will the momentum of a body change if its kinetic energy is doubled ?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 p = √2mK. When the kinetic energy K is doubled, the momentum p increases by √2 times its initial value.

-Answered by Shruti Srivastva On 14 July 2020:01:38:50 PM


Question 4. Asked on :14 July 2020:01:34:34 PM

 Show that 1 j = 107erg.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 1j = 1N X 1m = 105 dyne x 100cm = 107erg.

-Answered by Shruti Srivastva On 14 July 2020:01:35:29 PM


Question 5. Asked on :14 July 2020:01:32:08 PM

 Calculate the number of joules in 1 KWH.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 1 KWH = 1 KW X 1 H = 1000 Js-1 x 3600s = 3.6 x 106.

-Answered by Shruti Srivastva On 14 July 2020:01:33:02 PM


Question 6. Asked on :14 July 2020:01:30:37 PM

 Give SI unit of spring constant?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 SI unit of spring constant is Nm-1

-Answered by Shruti Srivastva On 14 July 2020:01:31:29 PM


Question 7. Asked on :14 July 2020:01:27:59 PM

 What is spring constant of a spring?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva
The spring constant of a spring is the restoring force set up in the spring per unit extension.

-Answered by Shruti Srivastva On 14 July 2020:01:29:06 PM


Question 8. Asked on :14 July 2020:01:23:44 PM

 State work-energy of theorem.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 According to work energy theorem, the work done by the net force acting on a body is equal to the change produced in the kinetic energy of the body.

-Answered by Shruti Srivastva On 14 July 2020:01:25:18 PM


Question 9. Asked on :14 July 2020:01:19:11 PM

 What is the source on the kinetic energy of the falling rain drops?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Potential energy of the falling rain drops changes gradually into their kinetic energy.

-Answered by Shruti Srivastva On 14 July 2020:01:22:30 PM


Question 10. Asked on :14 July 2020:01:17:06 PM

 Give two example from daily life where according to physics, work done is zero.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 (i) Work done by the earth's gravitational force in which keeping the moon in its orbit.

(ii) Work done by a man carrying a load in his head and walking along horizontal is zero.

-Answered by Shruti Srivastva On 14 July 2020:01:20:26 PM


Question 11. Asked on :14 July 2020:01:13:45 PM

 An artificial satellite is at a height of 36,500 km above earth's surface. What is the work done by earth's gravitational force in keeping in its orbit?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Zero, work done by earth's gravitational force in keeping in its orbit.

-Answered by Shruti Srivastva On 14 July 2020:01:18:36 PM


Question 12. Asked on :14 July 2020:01:11:19 PM

 How much work a man will do in carrying a 10 kg load over his head horizontally on smooth surface for 10 metres?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Zero, because force and displacement are perpendicular to each other.

-Answered by Shruti Srivastva On 14 July 2020:01:12:53 PM


Question 13. Asked on :14 July 2020:01:08:56 PM

 What is Einstein's energy-mass equivalence relationship?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 E = mc2 is Einstein's energy-mass equivalence relationship.

-Answered by Shruti Srivastva On 14 July 2020:01:10:24 PM


Question 14. Asked on :14 July 2020:01:06:43 PM

 Name the force in which momentum changes but K.E. does not change?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Work done by a man carrying a load on his head and walking along horizontal is zero.

-Answered by Shruti Srivastva On 14 July 2020:01:07:53 PM


Question 15. Asked on :14 July 2020:01:04:16 PM

 Name the force in which momentum is conserved nut K.E. is not conserved?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

Work done by the earth's gravitational force in keeping the moon in its orbit is zero.

-Answered by Shruti Srivastva On 14 July 2020:01:05:36 PM


Question 16. Asked on :14 July 2020:01:01:42 PM

 Friction is non-conservative force. how?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Work done against friction in any round path is never zero, hence friction is non-conservative force.

-Answered by Shruti Srivastva On 14 July 2020:01:02:39 PM


Question 17. Asked on :14 July 2020:01:00:07 PM

 Give three examples of forces which are conservative in nature.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Gravitational, electrostatic and magnetic force . 

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


Question 18. Asked on :14 July 2020:12:57:35 PM

 A bullet gets embedded into a block of wood, how does the loss of energy appear?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Kinetic energy of bullet gets converted into heat and sound energy.

-Answered by Shruti Srivastva On 14 July 2020:12:59:00 PM


Question 19. Asked on :14 July 2020:12:55:01 PM

 If two bodies stick together after collision, will the collision be elastic or inelastic?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

  If two bodies stick together after collision Inelastic collision takes place

-Answered by Shruti Srivastva On 14 July 2020:12:56:29 PM


Question 20. Asked on :14 July 2020:12:52:05 PM

 What is that physical quantities which is conserved both in elastic and inelastic collisions?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Linear momentum is conserved both in elastic and inelastic collisions.

-Answered by Shruti Srivastva On 14 July 2020:12:54:32 PM


Question 21. Asked on :14 July 2020:12:45:50 PM

 What is a conservative force ?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 A force is said to be conservative, if the amount of work done in moving an object against the force depends only on the initial and the final positions of the object. 

-Answered by Shruti Srivastva On 14 July 2020:12:46:29 PM


Question 22. Asked on :14 July 2020:12:44:01 PM

 When a planet revolves round the sun, when is its kinetic energy maximum?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 When the planet is nearest to the sun.

-Answered by Shruti Srivastva On 14 July 2020:12:45:18 PM


Question 23. Asked on :14 July 2020:12:40:35 PM

 Is physical quantity of power is a scalar quantity or a vector quantity?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 It is a scalar quantity .

-Answered by Shruti Srivastva On 14 July 2020:12:43:32 PM


Question 24. Asked on :14 July 2020:12:38:29 PM

 Name the physical quantity which is expressed as force times velocity. 

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 The physical quantity is power.

-Answered by Shruti Srivastva On 14 July 2020:12:40:08 PM


Question 25. Asked on :14 July 2020:12:36:37 PM

 How many watts are there in one horse power?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 1 Horse power = 746 watt. 

-Answered by Shruti Srivastva On 14 July 2020:12:38:00 PM


Question 26. Asked on :14 July 2020:12:32:41 PM

 What are the dimensions off power?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 [Power] = [ML2T-3].

Dimension of power.

-Answered by Shruti Srivastva On 14 July 2020:12:33:38 PM


Question 27. Asked on :14 July 2020:12:30:52 PM

 Is the unit watt second associated with energy or power?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Watt second is the unit of energy.

-Answered by Shruti Srivastva On 14 July 2020:12:32:14 PM


Question 28. Asked on :14 July 2020:12:28:38 PM

 Define the SI unit of power?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 The SI unit of power is watt. If an agency does work at the rate of 1 joule per second, its power is 1 watt.

-Answered by Shruti Srivastva On 14 July 2020:12:29:43 PM


Question 29. Asked on :14 July 2020:12:27:15 PM

 Define power?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Power is the rate of doing work.

-Answered by Shruti Srivastva On 14 July 2020:12:28:11 PM


Question 30. Asked on :13 July 2020:06:41:19 PM

 A spring is cut into two halves. How is the spring constant of each half affected?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Spring constant of each half becomes twice the spring constant of the original spring.

-Answered by Shruti Srivastva On 13 July 2020:06:42:37 PM


Question 31. Asked on :13 July 2020:06:38:30 PM

 What kind of energy transformation takes place at a hydro-electric power house? 

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Potential energy of water changes into K.E. and then into electrical energy.

-Answered by Shruti Srivastva On 13 July 2020:06:39:59 PM


Question 32. Asked on :13 July 2020:06:36:34 PM

 When an air bubbles rise in water, what happens to its potential energy?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Potential energy of air bubbles decrease.

-Answered by Shruti Srivastva On 13 July 2020:06:37:50 PM


Question 33. Asked on :13 July 2020:06:34:58 PM

 What kind of energy is stored in the spring of a watch?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Potential energy is stored in the spring of a watch.

-Answered by Shruti Srivastva On 13 July 2020:06:35:57 PM


Question 34. Asked on :13 July 2020:06:32:23 PM

 Is the mechanical energy always conserved?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 No. The mechanical energy is conserved only when conservative forces are involved and that too in a an isolated system.

-Answered by Shruti Srivastva On 13 July 2020:06:33:16 PM


Question 35. Asked on :13 July 2020:06:29:53 PM

 Out of joule, calorie, kilowatt and electron vott, which one is not the unit of energy?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Kilowatt, which is the unit of power and not of energy.

-Answered by Shruti Srivastva On 13 July 2020:06:31:20 PM


Question 36. Asked on :13 July 2020:06:28:01 PM

 Can the P.E. of a body be negative.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Yes, the potential energy is negative when forces involved are attractive.

-Answered by Shruti Srivastva On 13 July 2020:06:28:58 PM


Question 37. Asked on :13 July 2020:06:23:28 PM

 Does a man standing at rest on a moving car possesses kinetic energy?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Yes, because the man forms part of the moving car and so he possesses kinetic energy.

-Answered by Shruti Srivastva On 13 July 2020:06:24:43 PM


Question 38. Asked on :13 July 2020:06:22:08 PM

 Has an object in motion ability to do work?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Yes, becauise an object in motion possesses kinetic energy.

-Answered by Shruti Srivastva On 13 July 2020:06:22:51 PM


Question 39. Asked on :13 July 2020:06:19:10 PM

 Does the work done depend on how fast or slow a body is moved?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 No, The work done is independent of time n which the work is completed.

-Answered by Shruti Srivastva On 13 July 2020:06:20:22 PM


Question 40. Asked on :13 July 2020:06:16:09 PM

 Give an example in which a force doe work on a body fails to change its Kinetic energy.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 When a body is pulled on a rough horizontal surface with constant velocity, work is done by the applied force on the body but K.E. of the body remains uncharged.

-Answered by Shruti Srivastva On 13 July 2020:06:17:27 PM


Question 41. Asked on :13 July 2020:06:13:44 PM

 A man runs a distance on a level road. The same man ascends up a hill with the same velocity through the same distance. When does he do more work?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 More work is done in the second case.

-Answered by Shruti Srivastva On 13 July 2020:06:15:30 PM


Question 42. Asked on :13 July 2020:06:11:20 PM

 Find the number of joules in the gravitational unit of work in SI.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 1 kg m = 1 kg wt x 1 m = 9.8 N x 1 m = 9.81j.                                                     

-Answered by Shruti Srivastva On 13 July 2020:06:12:29 PM


Question 43. Asked on :13 July 2020:06:04:49 PM

 State gravitational unit of work in SI.

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 In SI, the gravitational unit of work done is one kilogram metre. It is defined as the  work done when a force of one Kilogram weight displaces a body through a distance of one kilogram weight displace a body through a distance of one metre in its own direction. 

-Answered by Shruti Srivastva On 13 July 2020:06:06:23 PM


Question 44. Asked on :13 July 2020:06:01:01 PM

 What do you mean by gravitational unit of work?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Work done is said to be one gravitational unit if a force of one gravitational unit displace a body through unit distance of one kilogram weight displaces a body through a distance of one metre in its own direction.

-Answered by Shruti Srivastva On 13 July 2020:06:01:45 PM


Question 45. Asked on :13 July 2020:05:58:39 PM

 How many joules make up one erg?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 As    107 erg = 1 joule, 

therefore , 1 erg = 10-7 joule.

-Answered by Shruti Srivastva On 13 July 2020:05:59:48 PM


Question 46. Asked on :13 July 2020:05:54:32 PM

 Define SI unit of work?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 One Joule of work is said to be done when a force of one newton displaces a body through a distance of one metre in its own direction. 

-Answered by Shruti Srivastva On 13 July 2020:05:55:16 PM


Question 47. Asked on :13 July 2020:05:51:51 PM

 Name the SI unit of unit?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 The SI unit of work is joule (J).

-Answered by Shruti Srivastva On 13 July 2020:05:53:54 PM


Question 48. Asked on :13 July 2020:05:49:35 PM

 Moment of a force and work done by a force have same units. What is the difference between them?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Moment of force is a vector quantity while work done is a scalar quantity.

-Answered by Shruti Srivastva On 13 July 2020:05:50:49 PM


Question 49. Asked on :13 July 2020:05:47:04 PM

 What physical quantity does the area under the force-displacement curve represent?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 The area under the force-displacement curve represents the work done by the force over the given displacement.

-Answered by Shruti Srivastva On 13 July 2020:05:48:20 PM


Question 50. Asked on :13 July 2020:05:45:08 PM

 Is work done a scalar or a vector quantity?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Scalar quantity, because work can be expressed as the scalar product of force and displacement vectors.

-Answered by Shruti Srivastva On 13 July 2020:05:45:55 PM


Question 51. Asked on :13 July 2020:05:41:44 PM

 What is the work done by the force of tension in the string of simple pendulum?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Zero, because the tension in the string of a simple pendulum is always perpendicular to its displacement. So, the work done by the tension is zero.

-Answered by Shruti Srivastva On 13 July 2020:05:43:38 PM


Question 52. Asked on :13 July 2020:05:38:26 PM

 State the conditions under which a force does not work?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 (i) The displacement is zero, or

(ii) The displacement is perpendicular to the force, or

(iii) The conservative force moves a bodu over a closed path.

-Answered by Shruti Srivastva On 13 July 2020:05:39:58 PM


Answer:

Shruti Srivastva

 The revolution of satellite around the earth.

-Answered by Shruti Srivastva On 13 July 2020:05:39:23 PM


Question 54. Asked on :13 July 2020:05:32:42 PM

 What should be the angle between the directions of force and displacement for maximum and minimum works?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 (i) For minimum work, Θ=0°

(ii) For maximum work, Θ=90°

-Answered by Shruti Srivastva On 13 July 2020:05:34:03 PM


Question 55. Asked on :13 July 2020:05:27:27 PM

 What do mean by work done by a force?

-Added by Shruti Srivastva Physics » Work, Energy And Power

Answer:

Shruti Srivastva

 Work is said to be done whenever a force acts on a body and the body moves in the direction of the force.

-Answered by Shruti Srivastva On 13 July 2020:05:28:26 PM


 

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