Work = Force x Distance W= F x d Work is a force exerted across a distance ! A transfer of energy!

Additionally… The force and the movement must be in the same direction.

The weight-lifter holds the weight over his head. Is he doing work? NO! There is no change in distance!

W= F x d F = Newtons (N) d = meters (m) W = N · m or Joule (J)

W= F x d How much work is done by a crane that raises 1000 N of material a distance of 150 m? W = F x d = 1000 N x 150 m = 150,000 J

A force of 10,000 N is applied to a stationary wall. How much work is performed? W = F x d = 10,000 N x 0 m! = 0 J! No work is done because there is no movement!

We can compare the work we put into a machine and the work we get out of it to determine a machine’s efficiency

A person applies a force of 200 N over 1.5 m to a jack. The jack exerts a 1000-N force on a car a distance of 0.02 m. What is the efficiency rating of the jack?

A student uses a manual air pump to inflate his basketball. He applies 235 J of work to the pump. The pump releases air by doing 170 J of work. How efficient is the air pump?

Can a machine ever be more than 100 % efficient?

Power is the rate of work Power = Work = N · m or J time = s Power = Watt (W)

How can we increase power? Increase work …Increase force, increase distance… Decrease time

A 750-N person climbs to the top of a 4-meter ladder in 15 seconds. What is the person’s power?