# Coneceptual Exercise on Static Friction

1. Sep 18, 2010

### MozAngeles

1. The problem statement, all variables and given/known data
The three identical boxes shown in the figure remain at rest on a rough, horizontal surface, even though they are acted on by two different forces, F1 and F2. All of the forces labeled F1 have the same magnitude; all of the forces labeled F2are identical to one another.

Rank the boxes in order of decreasing magnitude of the force static friction between them and the surface.
Rank the boxes from highest to lowest magnitude of the force static friction between them and the surface. To rank items as equivalent, overlap them.

2. Relevant equations

3. The attempt at a solution
I thought it would be box 1, 3, then2 two but that it not right.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 18, 2010

### kuruman

Why makes you think that?

3. Sep 18, 2010

### MozAngeles

Well the F_1 on box one is pushing in the same direction as F_2 so, it had the most net force on it.. I thought. and the box two only has F_1 pushing down on it and F_2 pushing to the right.

4. Sep 18, 2010

### kuruman

Your answer is partially correct. Think in terms of horizontal components of the vector sum of F1 and F2 on each box. Which box has the largest total horizontal component on it? That's the box that needs the largest static friction to cancel it. Which box has the next largest horizontal component and which one has the least?

5. Sep 18, 2010

### MozAngeles

thank you that helped!