# Problem 13

1. Dec 10, 2006

### Iceclover

1. The problem statement, all variables and given/known data
a student librarian picks up a 22N book from the floor to a height of 1.25m. He carries the book 8.0m to the stacks and places the book on a shelf that is 1.35m high. How much work does he do on the book

2. Relevant equations

W=Fd

3. The attempt at a solution

Am i just supposed to add up all the distances and then use my W=Fd formula?

2. Dec 10, 2006

### PhanthomJay

Your formula for work is not quite correct. Only the component of the force in the direction of the displacement does work.For example, to find our how much work is done in carrying the book 8.0 meters to the stacks, answer the following question: How much force acts in the direction of the 8 meter displacement?

3. Dec 10, 2006

### Iceclover

what is the correct formula for work then?

4. Dec 10, 2006

### PhanthomJay

$$W = Fdcos\theta$$
where $$\theta$$ is the included angle between the force vector and the displacement vector.