Yet another two-block system question. I guess I don't understand this still.

  • Thread starter Bensky
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  • #1
Bensky
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Homework Statement


See attempt at solution. It has everything.


Homework Equations


F_net = ma (net force)
W = mg (weight)
f_k = u_k * N (frictional force - kinetic)

T is the tension force.

The Attempt at a Solution



See attachment below. I realize I just posted a problem related to a two block system. I got help on the last problem and thought I understood it completely, but this time I'm REALLY not sure what I'm missing. I checked over the coordinate system and all the signs in the problem and thought all my steps made sense. Am I simply missing a force?

The answer I should be getting is u_k = 0.25, but I get 0.583 instead.
 

Attachments

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Answers and Replies

  • #2
rl.bhat
Homework Helper
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For 10 kg block g*sinθ and ax are in the same direction. So in that equation you have to equate it to -m*ax.
 
  • #3
Bensky
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For 10 kg block g*sinθ and ax are in the same direction. So in that equation you have to equate it to -m*ax.

Thank you, that did give me the correct answer. Are you saying the acceleration should be negative on block A since it is traveling in the -x direction (left)?
 
  • #4
rl.bhat
Homework Helper
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Thank you, that did give me the correct answer. Are you saying the acceleration should be negative on block A since it is traveling in the -x direction (left)?
The mass is moving in the direction of g*sinθ. In the equation you have taken g*sinθ -ve, so ax also -ve.
 
  • #5
Bensky
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The mass is moving in the direction of g*sinθ. In the equation you have taken g*sinθ -ve, so ax also -ve.

What is "ve"?

EDIT: Nevermind, you mean -ve = "negative" haha. I'm a little slow tonight, nevermind! I understand, thanks.
 

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