Basic Physics Question

1. Nov 1, 2006

MattsVai

Hi everyone! This is my first post so I thought it appropriate to start with a basic question and not give u guys a hard time :) ehehe

So imagine u have 1 box resting on a larger box. A force is applied to this larger box and the smaller box moves with the larger box without slipage.

My question is, if I were to draw up the FBD, what forces are being applied on the small box apart from Fn and Fg?

Cheers

2. Nov 1, 2006

matthew baird

Well isn't that it?? Apart from a rediculously small amount of drag, which force do you suppose is keeping the small box from sliding off the larger one? that's your hint..

3. Nov 1, 2006

MattsVai

Well, I am thinking apart from Fn + Fg there is a friction force keeping that small box stationary on top of the larger box. If that is the case there must be a balancing force because technically the small box is relatively stationary. So this means that we also have the applied force Fa on the small box too?

This results in 4 forces: Fn, Fg, Fa, Ff

Am I on the right track?

4. Nov 1, 2006

matthew baird

You are right to think that there is an equal/opposite of the static friction on the small box, but that force acts on the big box.
So, a revised list would be:
Fn,Fg,Fs where Fs=force of static friction

5. Nov 1, 2006

MattsVai

Makes sense... thanks a bunch :)