More physics..Help!?

Question

A 100.0 kg commuter is standing on a train accelerating at 3.70 m/s^2. What coefficient of friction must exist between the commuter's feet and the floor to avoid sliding?

Can anyone help me with this? Can you show me how to solve this, or even what the answer is? Help! Thanks a lot.

Answer 1

Force causing acceleration F is countered by the force of friction f.
F=f
ma= umg

u= a/g = 3.70/9.81=0.377