I am not properly educated on this, but I do know you are always meant to lift and set things down by using your legs to either heighten or lower yourself and the item. You would do this by squatting, grabbing the item, and returning to a standing position, the opposite goes for setting it back down. Do NOT use your back, so don't bend over to do this.
Answer:

Explanation:
= Coefficient of friction
g = Acceleration due to gravity
m = Mass of box = 
a = Acceleration of the block = 
Acceleration is given by

Friction force is given by

The magnitude of the force of friction on the box as it moves with the truck without slipping is
.
Answer:
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