Question

A body of mass 5 kg is moving with a velocity 10 ms-1. Find the ratio of initial kinetic and
final kinetic energy if its velocity is made three times?​

Answer 1

Answer:

1:9

Explanation:

Let the initial kinetic energy be Kₓ.

Let the final kinetic energy be Kₐ

Kₓ : Kₐ

$\frac{1}{2}(5)(10)^{2} : \frac{1}{2}(5)(3X10)^{2} \\\\\frac{1}{2}(5)(10)^{2} : 9 X \frac{1}{2}(5)(10)^{2}\\\\1:9$

Answer 2

We have,

Mass of body = 5 kg

Velocity = 10 m/s

Final velocity = 3(10 m/s)

We know,

$\boxed{KE = \frac{1}{2} mv^2}$

∴ Ratio = $\frac{\frac{1}{2} mu^2}{\frac{1}{2}mv^2}$

⇒ Ratio = $\frac{u^2}{v^2}$

⇒ Ratio = $\frac{u^2}{(3u)^2}$

(You can even put down the values, if you want to. The ratio can be obtained directly.)

⇒ Ratio = $\frac{u^2}{9u^2} = \frac{1}{9}$

⇒ Ratio = $1:9$ (Answer).