A 32 kg child uses a pogo stick to bounce up and down. The spring constant, k, of the toy equals 9,400 N/m. (a) By how much would the spring be compressed by the child if she simply balanced herself vertically on the pedals of the stick? (Give your answer in cm.)
33
x cm
(b) How much energy (in )) is stored in the spring under this circumstance?

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.