A 400 kg baby grand piano is raised to the roof of a 100 m building. If the cable breaks as it reaches this height, what will its velocity be the instant prior to impact? Use energy considerations and verify using kinematics.
(a) using dynamics
mgh=mv²/2
v=sqrt(2gh)
(b) using kinenatics
h=gt²/2 =>sqrt(2h/g)
v=gt=gsqrt(2h/g)=sqrt(2gh)