What is work?The Meaning of work, calculating work &

power

workWork is done on an object when the object moves in the same direction in which the force is exerted.

Ex:Push a child on a swingPull your books out of your backpack

Lift a book

Work questionsPick up your backpack?Carried your backpack at school?Carry books to your desk?Pull open a door?Push your friend in the hall?Lift weights above your head?

Work done?Force is not in the direction motion.No work is done

Work done?Force is in thesame direction of motionWork is done!

Horizontal part of the force does work.

Calculating workWork = Force x DistanceLifting an object: the upward force

must be at least equal to the object’s weight.

When you lift a plant, you do work. If you exert a force of 50 N and lift the plant 0.5 meters, what is the work you do?

Work = 50 N x 0.5 m 25 Nm (Newton meters)

Demo: PinwheelIs work always the same?

Dryer on high settingObserve

pinwheel motionDryer on low

setting.Observe

pinwheel motion.

Explain why work is done on the pinwheel.

How are the two situations different?

Is the amount of work greater for the high or low setting?

Why?Where would you

infer the best locations for windmills to be placed to produce electricity?

powerWhat are some things you would describe as

powerful?What characteristics do all these things

share?

Power: the rate at which work is done.

rate?How much of something happens in a

certain time period.Power = work/timeUnit of power = J/s

Power QuestionsMore power to run up the stairs with your

backpack or walk ?Which has more power? Raking the leaves or

using a blower?Which does more work? Raking leaves or

using the blower?

PowerObject that has more power does more work in the same time.

orSame amount of work in less time.

Doing work?

Question AnswerAsking Questions

What is work?Work is done when an object moves in the same direction in which the force is exerted.

How can you calculate work? Work = Force X

Distance

What is power? Power is the rate at which work is done.