# Work and displacement physics problem

1. Nov 12, 2007

### grouchy

To keep her dog from running away while she talks to a friend. Susan pulls gently on the dog's leash with a constant force given by F = (2.2 N)i + (1.1 N)j . How much work does she do on the dog if its displacement is

a) d = (.25 m ) i
b) d = (.25 m ) j
c) d = (-.50 m)i + (-.25 m ) j

My main problem is whether or not I need to combine the force or simply W = Fd. Thx for any help

2. Nov 12, 2007

### Oerg

Well, if we assume that she exerts a force such that the dog remains stationary, the net work done is zero.

however, if the force she exerts brings the dog to her, the we must mutiply the force exerted in this direction with the magnitude of the displacement of the dog from her.

In your above question, you should find the magnitude of the force she can exert and then multiply it by the distance the dog is from her.

3. Nov 12, 2007

### catkin

I guess the d values in the question say the dog does not remain stationary.

4. Nov 12, 2007

### Shooting Star

Hi grouchy,

The problem implies that the dog underwent vector displacement d while the given force F was acting on it. Then work done is simply the dot product or the scalar product of F and d. I presume you know how to find that.