Calculating Work• Work = force (N) x distance (m)

• W = F x D

• The unit for work is a Joule (J).

• If you lifted an object weighing 1N through a distance of 1m, you did 1 Joule of work:

W = FD = 1N x 1m = 1 J

Think about how much force a Newton is…about ¼ of a pound. No!

Calculating Work

•If you lifted an object weighing 200 N through a distance of 0.5m, how much work would you do?

Calculating Work•If you lifted an object weighing 200 N through a distance of 0.5m, how much work would you do?

Work = force x distance = 200 N x 0.5m = 100 J.

Using stairs………..

Using Elevator………

..

What is the main difference between going up using an elevator and using the stairs?

It is the “ Time “

When work done is related to time …….

WE call it

Power•Power is the rate at which work is done , or the amount of work per unit of time.

Two men can move a lot of sand using shovels…

…but a front-end loader can do it in less time…

…because the front-end loader has more POWER.

Power•Power is the rate at which work is done , or the amount of work per unit of time.

•Power = work / time or

•Power = force x distance / timeBecause work = force x distance

Power•The unit for power is watt (W). One watt is equal to 1 joule per second (1 J/sec).

•Large quantities of power are measured in kilowatts (kW).

•One kilowatt equals _____ watts.1000