A ball of mass 1 kg thrown upwards reaches a maximum height of 5.0m. Calculate the work done by the force of gravity during this vertical displacement.

The force of gravity on the ball is

F=m g = (1 kg) (9.8 m/s²) = 9.8 N.

The displacement of the ball is d=5.0 m.

The force and the displacement are in opposite directions.

Hence, W = - F d

= - (9.8 N) (5.0 m) = - 49 J.

We can also say that a work of 49 J has been done against the force of gravity.