A 9 kg model airplane flies horizontally at a constant speed. If the plane suddenly dives from its altitude of 50 m and levels off at 20 m, how much potential energy does it lose in the dive?

Aheavy piece of hanging sculpture is suspended by a90-cm-long, 5.0 g steel wire. when the wind blows hard, the wire hums at its fundamental frequency of 80hz. what is the mass of the sculpture?