# Homework Help: Having trouble with a simple question

1. Feb 14, 2004

### MalusIgnis

Hi, I'm sure this will be considered a pretty stupid question. It's a simple physics problem, but I'm really not very good at physics :(

Anyway, here's the question:
Three blocks (m1, m2, and m3) are on a horizontal frictionless surface. A force of 18N is applied to the m1 block. These blocks are touching by the way...

What happens when this force acts on m1?
I need to find the acceleration of the three blocks, the net force on each block, and the magnitudes of the "contact forces" between the blocks.

I dont even know where to start... Is anyone interested in giving me some assistance? I dont want the question to just be answered, just some hints of where to go from here would be appreciated.

Thank you very much

2. Feb 14, 2004

### Chi Meson

If you push on this "train" of blocks, you can be certain that they all accelerate at the same rate, OK? That is, all blocks move together as one.

Since they all act as one, treat them as one object to find the acceleration: a = F/m , where m is the total mass and F is the force of your push.

Now you have the acceleration. Now you look at the force on block 2. What pushes on block 2? Block one does! HOw much force? same formula, except now its the force on block 2 and the mass of blocks 2 & 3 (the mass of block one does not count now, because this the is object doing the pushing).

Look at block 3 now. same accelleration. mass of block 3. what force?

3. Feb 14, 2004

### MalusIgnis

thanks for replying =) I think I figured it out actually...
rest assured, I"ll have many more questions in the future =)