A horizontal 90 kg merry-go-round is a solid disk of radius 1.50 m and is started from rest by a constant horizontal force of 50.0 N applied tangentially to the edge of the disk. The kinetic energy of the disk after 3.00 is

From the rigid object under a net torque model,∑τ=Iα→α=∑τl=FR12MR2=2FMRFrom the definition of rotational kinetic energy and the rigid object under constant angular acceleration model,K=12Iω2=12Iωi+αt2=12Iα2t2=1212MR22FMR2t2=F2t2M Substituting, K=(50.0N)2(3.00s)2(90.0kg)=250J