A 1.50 kg snowball is fired from a cliff 11.5 m high. The snowball's initial velocity is 16.0 m/s, directed to `41.0^(@)` above the horizontal . (a) How much work is done on the snowball by the gravitational force during its flight to the flat ground below the cliff ? (b) What is the change in the gravitational potential energy of the snowball-Earth system during the flight ? (c) If that gravitational potential energy is taken to be zero at the height of the cliff, what is its value when the snowball reaches the ground ?

Answer

(a) 169 J ; (b) - 169 J ; (c) The potential energy when it reaches the ground is less than the potential energy when it is fired by `|Delta U|`, so `U = - 169` J when the snowball hits the ground.