# Homework Help: Friction problem again Okay today is not my day

1. Sep 11, 2008

### vysis

1. The problem statement, all variables and given/known data

A passennger is standing without slipping in a forward accelerating train. The coeffeciant of the feet and the floor is 0.47. Determine the maximum required acceleration of the train relative to the track if the passenger is not to slip

2. Relevant equations

F=ma

3. The attempt at a solution

I know that acceleration = 0, but when I rearrange the equations. I end up with
F(a) = ma + (mu)mg. But I only know (mu)... so I end up not being able to solve it.

2. Sep 12, 2008

### alphysicist

If you consider things from the reference frame of the ground, the man is accelerating with the same acceleration as the train. Write out Newton's law in that case. What forces are acting on him? Once you use that in Newton's law, you should find that you only have one unknown left in your equation.

3. Sep 13, 2008

### vysis

but I'm not given the train's acceleration... am I missing something here =/?