# Homework Help: Frictional Forces

1. Dec 14, 2005

### grief

if I have a pieace of paper, a massive object resting ontop of it, and I pull the paper, am I exerting a force only on the paper or on the object on top of it? Or does the object on top have only friction acting on it?

2. Dec 14, 2005

### Astronuc

Staff Emeritus
You are exerting a force directly on the paper, and that force will equal the force which is the sum of forces of friction between the paper and the table, which is related to the mass on top of the paper.

If the paper is not moving then the force will be given by the product of static coefficient of friction (between paper and surface supporting it) and the weight on the paper. If the paper is moving then it will product of dynamic coefficient of friction (between paper and surface supporting it) and the weight on the paper, plus the product of the mass and whatever acceleration is applied to the mass. If the paper is pulled abruptly, the force will be the sum of the friction between the paper and supporting surface and the friction between paper and mass.

3. Dec 14, 2005

### grief

so when you say the acceleration applied to the mass, is that the same as the acceleration applied on the paper?

4. Dec 15, 2005

### Astronuc

Staff Emeritus
In the case where the mass remains in contact with the paper, and does not move with respect to the paper.