Work and PowerWork and Power

WorkWork

Work happens when a force moves Work happens when a force moves an object over a distancean object over a distance

If the object does not move, no work If the object does not move, no work is doneis done

For work to be done, the direction of For work to be done, the direction of the applied force must be the same the applied force must be the same as the direction of the motionas the direction of the motion

WorkWork

You lift a bag of groceries You lift a bag of groceries from the trunk of your carfrom the trunk of your car

Is work being done?Is work being done?You are using force to lift You are using force to lift

the bag of groceries, and the force is the bag of groceries, and the force is in the direction of the motionin the direction of the motion

WorkWork

You carry a bag of groceriesYou carry a bag of groceriesfrom the car to the kitchen from the car to the kitchen

Is work being done?Is work being done?You are using force to carryYou are using force to carry

the groceriesthe groceriesIs the force being applied in the Is the force being applied in the

direction of the motion?direction of the motion?

Calculating WorkCalculating Work

Work = force x distance movedWork = force x distance movedW=FW=FΔΔd (on your reference table!)d (on your reference table!)Units of work are N·m, Units of work are N·m,

Also known as the jouleAlso known as the jouleAbbreviated JAbbreviated J

Set up the triangle!Set up the triangle!

Calculating WorkCalculating Work

Work

Force Distance

Work PracticeWork Practice

60N of force is used to move an 60N of force is used to move an object a distance of 4.0m. How much object a distance of 4.0m. How much work has been done on the object?work has been done on the object?

Work PracticeWork Practice

When you pick up your backpack, you When you pick up your backpack, you do 58J of work to lift it up 1.3m to put do 58J of work to lift it up 1.3m to put it on your back. What is the force on it on your back. What is the force on the backpack?the backpack?

Work PracticeWork PracticeA tow truck tows your car 2200m to A tow truck tows your car 2200m to

the nearest service station. If the the nearest service station. If the truck did 2,970,000J of work to tow truck did 2,970,000J of work to tow the car, what was the force on the the car, what was the force on the car?car?

Work PracticeWork PracticeA crane lifts a steel beam with 5200J A crane lifts a steel beam with 5200J

of work. If the force on the beam is of work. If the force on the beam is 240N, what is the distance the beam 240N, what is the distance the beam has been lifted?has been lifted?

PowerPower

The Power TriangleThe Power Triangle

Work

Power Time

PowerPowerWhere have you heard of watts Where have you heard of watts

before?before?Electrical energyElectrical energyLight bulbsLight bulbs

Can you explain why a bulldozer has Can you explain why a bulldozer has more power than a person with a more power than a person with a shovel?shovel?

Work and Power Tune

Calculating PowerCalculating Power

Espen and Deion push a sofa across Espen and Deion push a sofa across a room in 16 seconds using 142J of a room in 16 seconds using 142J of work. How much power did they work. How much power did they use?use?

Calculating PowerCalculating Power

KJ uses 72J of work to push a KJ uses 72J of work to push a textbook across the table. He uses textbook across the table. He uses 432W of power. How long did it take 432W of power. How long did it take him to move the book?him to move the book?

Calculating PowerCalculating Power

Aniké and Alanah move the lab table Aniké and Alanah move the lab table for 3 seconds using 98W of power. for 3 seconds using 98W of power. How much work did they do?How much work did they do?

Calculating PowerCalculating Power

Brynne throws a 12N softball 4m in Brynne throws a 12N softball 4m in 1.8s. How much power has she used 1.8s. How much power has she used on the softball?on the softball?