You push a crate full of nooks across the floor at a constant speed of 0.5 meter per second. You then remove some of the books and push exactly the same as you did before. How does the crate’s motion differ, if at all?

1 Answer
Feb 6, 2018

I would say that the crate now is accelerated.

Explanation:

During the first part you exert the exact force #vecF# to maintain the box in uniform motion, i.e., constant velocity (acceleration#=0#). In doing so you are winning against kinetic friction #f_k# but just! So your force and friction balance (almost) so that there is no acceleration but only constant velocity.

When you remove some books the box becomes lighter so that the normal reaction #N# decreases as well reducing the contribution of kinetic friction. Now if you push with the same force as before you face less friction so that you get a component of force that gives you acceleration!

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