Question

A 0.9 kg hollow ball with a radius of 0.12 m, filled with air, is released from rest at the bottom of a 2.0 m deep pool of water. How high above the water does the ball shoot upward? Neglect all frictional effects, and neglect the ball's motion when it is only partially submerged.

Neglect friction? Egads.

The average force on the ball is..

avg force=bouyancy at 1 m
= weightof water displaced - .9kg*g
= densitywater*4/3 PI r^3 - .9kg*g

Energy put in the ball= avg force(2m)

PE at top above water= .9g h solve for h.