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Understanding solution method for finding accelerations in a mechanical linkage

  • #1
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Homework Statement


I was checking my work and Chegg uses the equations differently. Can somebody tell me why? Maybe I'm misunderstanding how/why to use the equation I chose.
Steps 1-3.JPG
Steps 4-5.JPG



Homework Equations


They say aB = -ω2ABRB/Ai
I used aB = aA + αk x r - ω2rB/A

The Attempt at a Solution


So obviously mine will be a different answer, I only found aB but it gave me an i and j component because of that cross product. Which one is correct and why? Why can they neglect the cross product?
 

Answers and Replies

  • #2
TSny
Homework Helper
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The cross product term involves angular acceleration of the rod connecting A and B. In the Chegg problem, the angular acceleration is apparently zero.
 
  • #3
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How do they justify there being no angular acceleration? It doesn't say this is a static situation, so these bars should be rotating towards one another.
 
  • #4
169
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How do they justify there being no angular acceleration? It doesn't say this is a static situation, so these bars should be rotating towards one another.
I figured it out. The problem states that the velocities are constant and therefore the angular accelerations are zero.
Man, reading is important. Thank you for explaining this to me!
 

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