$(a)$ Define the term 'average power'.
$(b)$ When a player hits a football,it moves along a curved path and then falls to the ground. Calculate the work done by the force of gravity on the football.
$(c)$ Two friends,Ram and Shyam,each having a mass of $40 \, kg$,go for rock climbing. Ram climbs to a height of $3 \, m$ in $10 \, s$ and Shyam covers the same height in $12 \, s$. Is the work done by Ram and Shyam equal or not? Compare the power of Ram and Shyam.

(C) Average power is defined as the ratio of total work done to the total time taken.
$(b)$ When a football is kicked,it follows a curved path and returns to the ground. The work done by gravity depends only on the vertical displacement. Since the initial and final vertical positions are the same (ground level),the net vertical displacement $h = 0$. Therefore,the work done by gravity $W = mgh = 0$.
$(c)$ Work done by Ram and Shyam is equal because both have the same mass $(40 \, kg)$ and climb the same vertical height $(3 \, m)$.
Power of Ram $= \frac{mgh}{t} = \frac{40 \times 9.8 \times 3}{10} = 117.6 \, W$.
Power of Shyam $= \frac{mgh}{t} = \frac{40 \times 9.8 \times 3}{12} = 98 \, W$.
Since $117.6 \, W > 98 \, W$,the power of Ram is greater than the power of Shyam.