Question

A 200.0 kg piano is elevated by a crane to a height of 10.0 meters above a sidewalk. If the rope holding the piano breaks, what will the potential energy of the piano be when it has fallen 5.00 meters?

a) 0 J
b) 9,810 J
c) 10,000 J
d) 19,620 J

Answer 1

All that business about the crane and the rope and the falling
is only there to confuse us.

The piano ended up 5 meters above the ground.

           Potential energy = (mass) (gravity) (height)

                                   = (200 kg) (9.81 m/s²) (5 m)

                                   = (200 · 9.81 · 5)  (kg-m²/s²)

                                   =   9,810 joules   .