Question

Suppose that you are standing on a train accelerating at 0.20g. What minimum coefficient of static friction must exist between your feet and the floor if you are not to slide.

Answer 1

Friction force and train accelerating force are opposite in direction and equal in magnitude. Therefore m x a = u x m x g

As the mass is same, hence both are cancel out and remaining equation is

a = u x g

It’s given that a = 0.20g, so

0.20g = u x g

Cancel “g” on both sides;

0.20 = u

Thus the coefficient of static friction = u = 0.20