An electric motor and a single-fixed pulley work together to lift a 1,000 kg crate 50.0 m. how much work was done?

a) 50,000 j
b) 20 j
c) 500,000 j
d) 1,000 j

  C)  500,000 J

The change in potential energy is ...

  Mgh = (1000 kg)(9.8 m/s^2)(50 m) = 490,000 J . . . . roughly matches C

Comments on the problem

The efficiency of the motor is unknown, so the amount of energy spent as heat is unknown.

In the equation above, we have used M for mass, and m for meters. The acceleration due to gravity is approximately 9.8 m/s^2, varying depending on location and height above the Earth. The "standard" value for g will add a few more joules to this value, but will not make it 500,000.

compass can be used day and night, cloudy or sunny