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A small box of mass m1 is sitting on a board of mass m2 and length L. The coefficient of kinetic friction between the board and the horizontal floor is μk . The coefficient of static friction between the board and the box is μs.
At this moment, the board slides to the right along the surface, while the box does not slide on the board. What is the maximum magnitude of the force F pulling the board so that the box does not slip on the board?
* the answer key is (Us + Uk)(m1 + m2)g, I don't know how to get here.
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I don't understand why Fs <= Fk.
What does the F in (1) and (2) stand for? If it's force applied, wouldn't F = Fs + Fk for box 2, and (F - Fs - Fk) = Fs for box 1? My thinking is that the Force applied on box 2 minus the force of kinetic friction and the force of static friction applied by Box 1 on 2 would equal to the net force. Then the net force of box 2 would cause the same netforce on box 1, if box 1 isn't moving, then it's Fs should be equal to that net force applied on box 1. Therefore Force applied wouldn't be equal to Static
I don't understand why Fs <= Fk.
What does the F in (1) and (2) stand for? If it's force applied, wouldn't F = Fs + Fk for box 2, and (F - Fs - Fk) = Fs for box 1? My thinking is that the Force applied on box 2 minus the force of kinetic friction and the force of static friction applied by Box 1 on 2 would equal to the net force. Then the net force of box 2 would cause the same netforce on box 1, if box 1 isn't moving, then it's Fs should be equal to that net force applied on box 1. Therefore Force applied wouldn't be equal to Static
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