powerThe energy transferred each second, measured in watts (W). Power = work done ÷ time taken. 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.
Calculating power
To calculate power, use the equation:
\(power = \frac{work~done}{time~taken}\)
This is when:
power is measured in watts (W)
work done is measured in joules (J)
time taken is measured in seconds (s)
Example
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?
