1 Attachment(s)

Mechanics, linear motion help

Hi, this is probably something basic I am missing but I can't get my head around it.

Attachment 9544

In the question you are told that A and B are particles of mass 3m and m respectively, each attached to a light inextensionable string of length 3h. The string passes over a smooth pulley attached to a rough table. The coefficient of friction between the table and A is $\displaystyle u$.

The system is released from rest and begins to move...

1. Show that until B hits the floor, the acceleration of A is $\displaystyle \frac{1}{4}(1-3u)g$, this I was able to do.

2. Find the speed of A immediatly before B hits the floor, managed to do this as well, got it to be $\displaystyle \sqrt{\frac{gh(1-3u)}{2}}$

3. After B hits the floor, A continues to move, coming to rest before reaching the pulley. Deduce the range of values of $\displaystyle u$ for the motion above to be possible.

It is the last bit I can't get my head round, any ideas?

Thanks in advance

Craig