Optimizing Truck Deceleration to Prevent Crate Sliding

[Intrusionv2]

Homework Statement

A crate is sitting on the back of a truck at 20 m/s with a μ of 0.4. With what acceleration can the truck stop without having the crate slide?

Homework Equations

I'm not sure if I am supposed to use this equation:

a = μ(9.8)

The Attempt at a Solution

a = 0.4(9.8) = 3.92 m/s^2.

 

[Stovebolt]

That is correct, nice job.

 

[Intrusionv2]

So is the 20 m/s not needed?

 

[Stovebolt]

That is correct. You are only asked for acceleration (or deceleration in this case), so initial velocity doesn't come into play.