Two electric motors drive two elevators of equal mass in a three-story building 10 meters tall. Each elevator has a mass of 1,000 kg.

The first elevator can do this work in 5.0 seconds.

Calculate the power output of the first motor.

The answer is 19620 Watt = 19.62 kWatt

Power output (P) is work (W) divided by time (t) : P = W/t

A work (W) is a product of a force (F) and a distance (d) : W = F · d

Since the force is a product of mass and acceleration: F = m · a

then work would be: W = m · a · h

P = W/t

W = m · a · h

P = m · a · h / t

We have:

P = ?

m = 1000 kg

a = 9.81 m/s² (gravitational acceleration on the Earth)

h = 10 m

t = 5s

P = m · a · h / t = 1000 kg · 9.81 m/s² · 10 m / 5 s = 19620 Watt = 19.62 kWatt