Question

Two boys were playing with the same ball on a level ground. One of the boys throws the ball on the third floor of the building which is at a height of 5 m and the other boy manages to throw on the fourth floor which is at a height of 7 m from the level ground. Then the ratio of the potential energy gained by the ball in both cases is:

• A. 1: 1
• B. 2: 3
• C. 5: 7
• D. 3: 2

Answer 1

The correct option is C

5: 7

Let the mass of the ball be $m$ and heights be $h_1=5m$ and $h_2=7m$

Taking the ground level as the reference,

In the first case, the gain in gravitational potential energy ball would be = $m\times g\times h_1$

and for the other, it would be = $m\times g\times h_2$

The ratio of the potential energy would be equal to:

$\frac{m\times g\times 5}{m\times g\times 7}=5:7$