Momentum can be thought of as the product of mass and velocity. Momentum helps explain some of the most important interactions in nature.

Power is the rate at which energy is transferred or work is done. It has units of watts (W) or joules per second (J/s). The more energy that is transferred per second, or the more work that is done per second, the greater the power rating.

To calculate power, use the equation:

This is when:

- power is measured in watts (W)
- work done is measured in joules (J)
- time taken is measured in seconds (s)

A horizontal force of 50,000 N acts on a car, causing it to move a horizontal distance of 80 m in a time of 25 s. What is the power of the car?

First, find the work done on the car:

work done = force × distance

work done = 50,000 × 80

work done = 4,000,000 J

Then, find the power:

power = 4,000,000 ÷ 25

power = 160,000 W

- Question
A motor applies a force of 800 N to a trolley, causing it to move 80 m in a time of 16 s. What is the power of the motor?

Work done = 800 × 80

Work done = 64,000 J

Power = 64,000 ÷ 16

Power = 4,000 W