Question

A 950 kg sack of cement is li# ed to the top of a building 50 m high by an electric motor.
a Calculate the increase in the gravitational potential energy of the sack of cement. b The output power of the motor is 4.0 kW. Calculate how long it took to raise the sack to the top
of the building. c The electrical power transferred by the motor is 6.9 kW. In raising the sack to the top of the building,
how much energy is wasted in the motor as heat?

Answer 1

Answer:

a

Explanation:

a. potential energy = m x g xh = 950 x 9.8 x 50 j

b. power = work / time = potential energy / time

time = potential energy /power

= ( 950 x 9.8 x 50) / 4 x 1000 s

c. heat = power x time

= ( 6.9 - 4) 1000 x ( 950 x 9.8 x 50) / 4000J