A couple of problems on motion and force

[Gauss177]

Homework Statement

A flatbed truck is carrying a 3200-kg crate of heavy machinery. If the coefficient of static friction between the create and the bed of the truck is 0.65, what is the maximum rate at which the driver can decelerate when coming to a stop in order to avoid crushing the cab with the crate?

Homework Equations

fric = u*N
Fnet = m * a

The Attempt at a Solution

N = 3200*9.8 = 31360
fric = 0.65 * 31360 = 20384 N

thats as far as I got

 

[d_leet]

fricc= u*N*d*e I think

What are d and e? The frictional force is equal to the coefficient of friction, mu, times the normal force which is usually denoted by N.

 

[Fermat]

For 1), use Newton's 2nd law, F = ma. F is the decelerating force and the same force F acts on both the truck and the crate. But the actual force that slows down the crate is the force of friction between the crate and the floor of the truck. So what is the maximum frictional force you can have ?

2) is similar. Use F = ma and Fr = μm to get a. And minimum stopping distance comes from maximum decelerating (frictional) force.