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The drawing shows a large cube (m=25kg) being accelerated across a horizontal frictionless surface by a horizontal forceP. A small cube (m=4kg) is in contact with the fron surface of the large cube and will slide downward unlessPis sufficiently large. The coefficient of static friction between the cubes is 0.71. What is the smallest magnitude thatPcan have in order to keep the small cube from sliding downwards

I know that the weight of the small cube is 39.2N. I also know that Fn is in the same direction as P. Past that, I'm confused. I have a equation: F=u*Fn, which is friction is equal to coef. of friction times normal force.

Can someone explain to me what to do next?

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# Homework Help: Need help on friction problem

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