Calculating Acceleration of Blocks on a Ramp

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Homework Help Overview

The problem involves calculating the acceleration of blocks on a ramp, specifically focusing on the forces acting on blocks A, B, and C. The context includes static and kinetic friction coefficients and the weights of the blocks.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the setup of equations related to tension and forces acting on the blocks. There are attempts to derive acceleration and tension values, with some questioning the validity of their calculations.

Discussion Status

Some participants have provided guidance on the need to differentiate between weights and masses in calculations. There is ongoing exploration of the equations and their implications, with no clear consensus reached yet.

Contextual Notes

Participants are working under the constraints of specific weights and friction coefficients, and there is mention of an attached image that may provide additional context for the problem setup.

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Homework Statement


In Fig. 6-35, blocks A and B have weights of 51 N and 23 N, respectively. (a) Determine the minimum weight of block C to keep A from sliding if μs between A and the table is 0.23. (b) Block C suddenly is lifted off A. What is the acceleration of block A if μk between A and the table is 0.12?
**image is attached**

Homework Equations


fxnet= T-fs=ma
fymet= FN-Wc-Wa=0

fxnet=T-UkFn=ma

The Attempt at a Solution



I completed part (a) and got 4.8 to be the answer, however, I didnt get part (b), I tried to use the tension I got from part (a) and put it in the 3rd equation above and got -14,472 which is obviously not correct. Can anyone tell me what I'm doing wrong?
 

Attachments

  • Fig06_35.gif
    Fig06_35.gif
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The tension is not the same once things start accelerating. You'll have to set up equations for both masses and solve for the acceleration (and new tension).
 
Okay, I did that... the second two equations were Fxnet= T-Uk(WA)=ma and Fynet= Wb-T=ma and when I added them together I got Wb - Uk(Wa)=(ma + mb)a and then solved for a and got 0.23 for the answer, and it was yet again wrong. What am I doing that's not right again?
 
Be sure when calculating ma + mb that you are adding the masses and not the weights.
 

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