I have a few questions that i don't understand like how I am supposed to use a certain equation to solve it. Thank you for any help, it is greatly appreciated.

A man sees a 21.6 kg cart about to bump into a wall. The cart is moving a 1.6 m/s. If he grabs it when it is 0.5 m from the wall what is the mimum force he must apply to keep it from reaching the wall?

What is the mimum force required to start a 13.2 kg box moving across the floor if the coefficient of friction between the box and the floor is 0.48 ?

If a mimum force of 52 N is required to start a 17.8 box moving, what is coefficient of friction between the box and the floor?

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