Question

An electric motor takes 30 s to lift a box of mass 45 000g to a height of 1.7 m. Calculate the power of the electric motor.

Answer 1

Power P is the amount of energy E transferred or converted per unit time t, and is expression is:

P = E/t

The necessary energy to lift the box its the work of against the Gravity Force, and is given by:

E = mgh

Then the power is:

P = E/t

P = mgh/t

P = (45 kg)(9.8 m/s²)(1.7 m )/ 30

P = 24.99 W

P ≈ 25 W