Question

Two boys were playing with a 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 $5m$ and the other boy manages to throw on the fourth floor which is at a height of $7m$ from the level ground. The ratio of the work done by both the boys is?

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

Answer 1

The correct option is C

5: 7

The ratio of work done by both the boys is the respective change in gravitational potential energies of the ball. Taking the ground level as the reference, the gain in gravitational potential energy change for one ball would be $m\times g\times 5$ and for the other, it would be $m\times g\times 7$ after starting from a zero gravitational potential energy from the ground. The ratio of the work done would be equal to

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