State the meaning of work done.
A beach ball is let go from a balcony near the top of a tall building. The ball drops straight down from rest and later reaches a constant (terminal) speed. As it travels from the balcony to the ground, its gravitational potential energy falls by $60\ \text{J}$. The ball strikes the ground at a speed of $16\ \text{m s}^{-1}$ and has kinetic energy $23\ \text{J}$. Show that the mass of the ball is $0.18\ \text{kg}$.
Calculate the balcony's height above the ground.
Determine the average resistive force on the ball as it travels from the balcony to the ground.
State and explain how, if at all, the magnitude of the ball's acceleration in (b) changes during the time interval when the ball is moving downwards before it reaches constant (terminal) velocity.