°(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The figure shows two boxes, A and B, on a ramp. The ramp forms a 20° angle with the horizontal. Box A is in front of Box B and they are touching. Box A is 2 meters from the bottom of the ramp. The mass of A is 3 kg and the mass of B is 10.5 kg. The coefficient of kinetic friction for box A is .210 and the coefficient of kinetic friction for box B is 0.170.

How long will it take for A to reach the bottom of the ramp?

2. Relevant equations

F=ma

The kinematic equations

Force of Kinetic Friction=μ*n

No help needed! I solved it!

3. The attempt at a solution

I know that B is acting on A and A is acting on B. My problem is finding the net force between the two in the x direction. And then once I find that, I am having trouble finding an equation to use that will help me find how long it takes for A to reach the bottom.

I think that I might have found the correct net force but I'm not sure and I don't know what to do with that net force.

I've also drawn the two free body diagrams for the problem.

The Force that gravity exerts in the x direction on:

A=10.0554 N

B=35.1939 N

The force that the kinetic friction exerts in the x direction on:

A=-5.80166

B=-16.43804

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# Homework Help: Two boxes sliding down a 20° ramp.

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