Worked Example 01

The Question

You are helping a friend move into a new apartment. A box weighing 70 kg needs to be moved to make room for a couch. You are taller than the box, so you reach down to push it at an angle of 50 degrees from the horizontal. The coefficient of static friction between the box and the floor is 0.50 and the coefficient of kinetic friction between the box and the floor is 0.30.
  1. If you want to exert the minimum force necessary, how hard would you push to keep the box moving across the floor?
  2. Suppose you bent your knees so that your push were horizontal. How hard would you push to keep the box moving across the floor?

The Answer

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