Work and Power What is work Work is

Work and Power

What is work? Work is the product of force and distance Work is done when a force moves an object over a distance If an object does not move, no work is done. Work = Force x Distance (w = fd)

Work Requires Motion For a force to do work on an object, some of the force must act in the same direction as the object moves.

Work depends on direction • The amount of work done on an object depends on the direction of the force and the direction of the movement. • Any part of a force that does not act in the direction of motion does no work on an object.

Work examples Climbing stairs Pushing a shopping cart Lifting a weight

SI unit of work Joule One joule is the amount of work done when a force of 1 newton moves an object 1 m IN the direction of the force

Calculating Work = Force x Distance Force = 1600 N Distance = 2. 0 m Work = 1600 N x 2. 0 m Work = 3200 N*m = 3200 J

What is Power? Power is the rate of doing work. Doing work at a faster rate requires more power. To increase power, you can increase the amount of work done in a given time, or you can do a given amount of work in less time.

Calculating Power = Work SI unit = watt (W) Time Which is equal to one joule per second A 40 -watt light bulb requires 40 joules each second that it is lit

Calculating Power You exert a vertical force of 72 N to lift a box to a height of 1. 0 meter in a time of 2. 0 seconds. How much power is used to lift the box? Power = Work / Time Power = Force x Distance/ Time Power = 72 N x 1. 0 m / 2. 0 s

James Watt and Horsepower Another unit of power is horsepower One horsepower (hp) is equal to 746 watts James Watt first defined horsepower while looking for a way to compare the power outputs of steam engines he had designed. He defined horsepower based on the power output of a very strong horse.