Wellcome!

Question 1. Asked on :15 January 2019:05:44:19 PM

A bullet is fired from a rifle the kinetic energy of the rifle in comparison to that of the bullet is

-Added by Sumitra Mahajan Science » Force And Laws Of Motion

Himanshi Verma

a) more than one b) less than one c) equal to one d) zero

Let,
$M$ -mass of life
$v$- velocity of rifle
$m$ -mass of bullet
$u$ -velocity of bullet
$Mv=mu$
$\frac{{K}_{r}}{{K}_{b}}=\frac{\frac{1}{2}M{v}^{2}}{\frac{1}{2}m{v}^{2}}$
$\frac{\left(Mv{\right)}^{2}}{\left(Mu{\right)}^{2}}$$×\frac{m}{M}=\frac{m}{M}$
Since $m$ < $M$
${K}_{b}\phantom{\rule{thickmathspace}{0ex}}>\phantom{\rule{thickmathspace}{0ex}}{K}_{r}$
Therefore $\frac{Kinetic\phantom{\rule{thickmathspace}{0ex}}energy\phantom{\rule{thickmathspace}{0ex}}of\phantom{\rule{thickmathspace}{0ex}}rifle}{Kinetic\phantom{\rule{thickmathspace}{0ex}}energy\phantom{\rule{thickmathspace}{0ex}}of\phantom{\rule{thickmathspace}{0ex}}bullet}\phantom{\rule{thickmathspace}{0ex}}<\phantom{\rule{thickmathspace}{0ex}}1$
Hence b is the correct answer. Hence b is the correct answer.

-Answered by Himanshi Verma On 20 January 2019:05:18:11 PM

Question 2. Asked on :13 January 2019:04:49:55 PM

A tortoise moves a distance of 100m in 15min. What is its average speed in km/hr?

-Added by Himanshi Verma Science » Force And Laws Of Motion

Himanshi Verma

Given:  Tortoise moves 100 meters in 15 minutes.

Therefore, Average Speed = 100 meters /15 minutes

(as Speed = Distance/time)

= 0.10 Km/ 0.25 hours

(as 1 Km

= 1000 m and 1 hour = 60 min)

= 0.4 Km/hour

Answer – The average speed of tortoise is 0.4 Km/hour

-Answered by Himanshi Verma On 20 January 2019:05:13:43 PM

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