Work and PowerChapter 5 Section 1

WorkWork – transfer

of energy that occurs when a force makes an object move

WorkWork – transfer of energy that occurs when a

force makes an object move1. For work to occur, an object must move.2. The motion of the object must be in the same

direction as the applied force on the object.

Work and EnergyWork and

energy are related!!!

When work is done, a transfer of energy must always occur.

WorkWork is done on an object only

when a force is being applied to the object and the object moves.

Calculating WorkWork is equal to the force (in newtons) times

the distance (in meters)

Work = Force x distance

W = Fd

Example Problem:You push a refrigerator with a

force of 100 N. If you move the refrigerator a distance of 5 meters, how much work do you do?

Example Problem:You push a refrigerator with a force of 100 N. If

you move the refrigerator a distance of 5 meters, how much work do you do?

Step 1 Identify known and unknown values F = 100 N d = 5 m W = ???

Example Problem:You push a refrigerator with a force of 100 N. If

you move the refrigerator a distance of 5 meters, how much work do you do?

Step 2 Solve the problem W = Fd W = (100 N) (5 m) W = 500 J

PowerPower – the amount of work done in a certain

amount of time; rate at which work is done1. Calculating power – power equals work divided

by time2. Power is measured in watts (W)

Example Problem:You do 900 Joules of work in

pushing a sofa. If it took 5 seconds to move the sofa, what was your power?

Example Problem:You do 900 Joules of work in pushing a

sofa. If it took 5 seconds to move the sofa, what was your power?

Step 1 Identify the known and unknown valuesW = 900 Jt = 5 sP = ???

Example Problem:You do 900 Joules of work in pushing a

sofa. If it took 5 seconds to move the sofa, what was your power?

Step 2 Solve the problemP = __W__ = __900 J__ = 180 W

t 5 s