# Finding Acceleration of Two blocks connected by a string.

1. Apr 27, 2013

### shinify

1. Two blocks made of different materials connected together by a thin cord, slide down a plane ramp inclined at an angle θ to the horizontal. The masses of the blocks are mA and mB and the coefficients of friction are μA and μB.

PART A
If μA < μB, determine a formula for the acceleration of block A in terms of mA, mB, and θ.
PART B
If μA > μB, determine a formula for the acceleration of block A in terms of mA, mB, and θ.

3. I got Part A right, of which aA, 1= (mAgsinθ+mBgsinθ-AmAgcosθ-μBgcosθ)/(mA+mB)

For Part B, I attempted it to solve it, and got the same answer as I did in Part A, yet MasteringPhysics says this is incorrect. Am I doing anything wrong? "The correct answer does not depend on the variables: mA, mB, or μB. "

Thanks for the help in advance.

2. Apr 27, 2013

### Staff: Mentor

Hint: Do the blocks have the same acceleration?

3. Apr 27, 2013

### shinify

Oh, got it. I simply assumed that if μAB, then the blocks would end up touching each other and have the same acceleration;

I see now that's not the case. I got aA, 2= g(sinθ- μAcosθ). Thanks for your quick response and help, Doc Al!