1. Work

2. Definition Work is done on an object by a constant force moving the object through a distance It is the product of the displacement and the component of force parallel to the displacement

3. Equation W = F(//) x d d F θ W = Fdcosθ

4. Units W = F x d = N m 1 N m = 1 joule (J) Old British unit 1 J =.7376 ft lb

5. When Is There A Force and No Work? If object doesn’t move If force is perpendicular to the displacement, like carrying an object Cos θ = cos 90 = 0 Force acting must have at least some component in the same direction as displacement

7. Example A 50 kg crate is pulled 40 m along a horizontal floor by a constant force of 100 N which acts at an angle of 37° with the floor. The floor exerts a friction force of 50 N. Determine the work done by each force on the crate, and the net work done.

8. Example 2 a) Determine the work a hiker must do on a 15.0 kg backpack to carry it up a hill of a height of 10.0 m. Also determine b) the work done by gravity on the backpack and c) the net work done on the backpack