I'm not sure if I can post here, but I thought I saw a physics question here a time or two.

Here's my question:

A flatbed truck is carrying a 20.0-kg crate along a level road. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum acceleration that the truck can have if the crate is to stay in place?

Is the equation to solve for maximum acceleration F s,max= usN * us?

I was not taught how to do problems like this...not 100% sure what to plug in for usN...I gave it a shot:

The surface is flat, so I guess the normal force=20.0 kg, so I then mulitplied by .40 to get 8 m/s^2.........ahhhh. I don't know what I'm doing!