A container of mass 200 kg rests on the back of an open truck. If the truck accelerates t 1.5 m/sec2, what is the minimum coefficient of static friction between the container and bed of the track required to prevent the container from the sliding off the back of the truck.

To cause the crate to accelerate at 1.5 m/s^2 requires what amount of force to be applied to it? The only horizontal force being applied to the crate is friction with the truck bed, so set these equal. What do you get?