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I'm having trouble with this problem...

Two packages at UPS start sliding down the 20 degree ramp shown in the figure. Package A has a mass of 3.50 kg and a coefficient of kinetic friction of 0.200. Package B has a mass of 8.50 kg and a coefficient of kinetic friction of 0.130.

How long does it take package A to reach the bottom?

Picture is attached...

Now since both have different masses and friction coefficients I'm thinking they each take a different amount of time to reach the bottom. However because at the beginning they're an action/reaction pair I ADDED the x-component of weight for B to the forces acting on A when calculating the acceleration... then used kinematics :

[tex]x_f = x_i + v_i t + 1/2 a (t)^2[/tex]

where x final is 2 meters and initial x and v are zero and acceleration is the one I got from force analysis...

I've been at this problem for a few hours-- going back to it after every while and still have no idea on what to do. btw does it have calculus? It could be that. My professor puts in one or two questions with calculus in HW/midterm preperation questions but we never actually study physics problems with calculus. :(

thanks in advance for any help. :)

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# Homework Help: Newton's 3rd law

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