Science, Grade 6


Table Of Contents: Power

1. Work and Power
The amount of work that is accomplished is not related to time. For instance, during a five km bike ride, one person may pedal slowly, while another person may pedal quickly. In both cases, an equal amount of work is done. However, unlike work, power is affected by time. In this example, the more powerful cyclist is the one who pedals faster and arrives at the destination more quickly.
2. Definition of Power
Power is the rate at which work is done. A lawn mower that completes the job in 10 minutes is more powerful than a lawn mower that takes 30 minutes to complete the same job. Over the time period of an hour, the more powerful lawn mower can mow six lawns in an hour, while the less powerful mower can only mow two.
3. Calculating Power
Power is calculated by dividing the amount of work done by the amount of time it takes to do the work. Knowing that work equals force times distance, you can rewrite the equation as force times distance divided by time.
4. Power Example
Let’s calculate the power of a football player that uses 240 Newtons to move the training equipment 10 meters in 8 seconds. Using the equation for power to solve this problem, we learn that the power is equal to 300 Newton meters per second, or 300 joules per second.
5. A Watt Is a Unit of Power
Power is measured in units of joules per second, which are also known as watts. One thousand watts of power is equal to one kilowatt. Here are some examples of the amount of power required to run different household appliances and tools.