Here's the question: Two boxes are placed on top of one another. The top box has a weight of 20 N and the bottom box has a weight of 50 N. You can neglect friction between the bottom box and the floor, but uS = 0.5 and uK = 0.4. You can assume g = 10m/s^2. Both boxes are initially at rest.(adsbygoogle = window.adsbygoogle || []).push({});

a) you tie a string to the top box and exert a force F to the right so both boxes accelerate together to the right with the same acceleration. What is the maximum value of F for which the boxes have the same acceleration?

I did F = uS(m1 * g)

F = 0.5 (20N * 10m/s^2) = 100N

Is this right??

b) what if you pull witha force twice as large as the maximum value you calculated? Determine the acceleration of the box now. You should get two different values.

I did: 20 N = m1*a - uK(m1*g) and got 24 m/s^2

and m2*a = -uK(m1*g) and got -1.6 m/s^2

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# Homework Help: Box Problem Kinetic/Static Friction

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