A tennis ball of mass 60g is launched from ground level vertically upwards with a

speed of 30 m/s and reaches a height of 15m. Compute the loss of energy due to air

resistance.

I believe the loss of energy is equal to the work done. So i'm looking for force x distance

but am unsure about the force. My answer would be 60 x 9.8 x 15 but then why give me the speed