# The smallest coefficient of friction.

1. Sep 13, 2006

### Fittler

I just started with my Grade 12 Physics (Univeristy Level), and I would like some help (not necessarily an answer) but an explanation. Here it is:

A small box is resting on a larger box, which in turn sits on a table. When a horizontal force is applied to the larger box, both boxes accelerate together. The small box does not slip on the larger box.

If the acceleration of the pair of boxes has a magnitude of 2.5m/s/s, determine the smallest coefficient of friction between boxes that will prevent slippage.

I have drawn a free-body-diagram, and I have determined that the force of friction is what makes the small box move with the larger box. I do not have a teacher, other than for one period of the day for this course, so I will either have to wait to talk to him, or someone could pitch me something useful. Thanks.

2. Sep 13, 2006

### Hootenanny

Staff Emeritus
Welcome to the Forums,

You are quite right that it is the frictional force between the two boxes that prevents the smaller box moving. Now, you know that at the point of slippage the maximum static frictional force will equal the applied force. Can you write an equation to show this?