Explain what is meant by work done.
A ball of mass 
is dropped from the top of a building. The ball falls from rest through a vertical distance of 
to the ground. Air resistance is significant so that the ball reaches constant (terminal) velocity before hitting the ground. The ball hits the ground with a speed of 
.
Calculate, for the ball falling from the top of the building to the ground:
the decrease in gravitational potential energy.
the increase in kinetic energy.
Use your answers in (b)(i) to determine the average resistive force acting on the ball as it falls from the top of the building to the ground.
The ball in (b) is dropped at time 
and hits the ground at time 
. The acceleration of free fall is 
. On the figure below, sketch a line to show the variation of the acceleration 
of the ball with time 
from time to .
and the perpendicular displacement 
in the direction of the force.
.
.
.
