Name __________________________ Date ___________Line ________

The science definition of work is very different from our normal definition of work.

Two things must be true in order for work to be done

A person is pushing on a wall. He is

sweating hard and considers it hard work,

but why is this NOT WORK??

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A person carrying a stack of books while

walking. She is huffing and puffing and

considers it hard work, but why is this NOT

WORK??

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Let’s calculate work! Your work formula:

You push a refrigerator with a force of 100N. If you move the refrigerator a distance of 5m how much work is done?

Let’s calculate power!

You lift a crying baby from a crib with 50 J of work. It takes you 5 seconds. How much power is needed?

COMBINE BOTH FORMULAS: A person pushes a couch with 100 N of force. It moves 5 meters and it takes him 2 seconds to do this. What was his power?

Name __________________________________________ Date __________

A lawn mower is pushed with a force 1000 N. If 5000 J of work is done in mowing a lawn, what is the distance the lawn mower was pushed?

The brakes on a bike do 2000 J of work in stopping the car. If the car travels a distance of 100 m while the brakes are being applied, what is he force the brakes exert on the bike?

You push a box with a force of 20 N. It doesn’t move. What is the work done?

A light bulb converts electrical energy into light and heat at a rate of 75 J every second. How many watts is the light bulb?

If a runner’s power is 80 W, what is the work done by the runner in 5 seconds?

How long will it take a car motor to do 5000 J of work if it uses 50 W of power?

You lift a stack of books and do 200 J of work in 5 seconds. What is the power?

You toss a baseball in the air and use 50 W of power in 2 seconds. What is the work done?