A champion weightlifter raises a 200 kg set of weights from the floor to above his head in one movement. The bar is lifted through a vertical distance of 1.8 m. When the lift is completed the weightlifter holds the weights stationary for 2.0 seconds and then drops them to the floor. At what speed do the weights hit the floor?
(gravitational field strength = 10 N / kg)
Answer:
15) E
PE at the top of the lift = 200 x 10 x 1.8 = 3600 J
All PE is converted to KE just before contact with the ground.
½ mv2 = 3600
(200) v2 = 7200
v2 = 36
v = 6 m/s
