Physics
posted by Lindsay on .
A railroad flatcar is loaded with crates. The coefficient of static friction between the crates and the floor is 0.27. If the train is moving at 59.7 km/hr, in how short a distance can the train be stopped with a constant acceleration without causing the crates to slide?
I have noo idea how to do this. Can someone show me the steps?

friction between the crates and floor
Force= mu*mass*g
But that must equal ma, or m (v^2/(2d))
mu*mass*g= mass*v^2/2d and you are looking for d. 
How do I find the mass?

A railroad flatcar is loaded with crates. The coefficient of static friction between the crates and the floor is 0.27. If the train is moving at 59.7 km/hr, in how short a distance can the train be stopped with a constant acceleration without causing the crates to slide?
Ok so I understand that mu*mass*g= mass*v^2/2d, and I need to solve for d. But how do I get the mass? 
the masses cancel