I am in second year engineering and am trying very hard in this course. I just started doing problems regarding simple kinetics this morning and I am getting a lot of wrong answers. Originally I just claimed to myself that I had made simple math errors but understood the concepts. The math in this question is simple enough, I have checked my math over many times with no success. I am getting kind of discouraged and was wondering if someone would be so kind to make sure I am setting up my equations correctly.(adsbygoogle = window.adsbygoogle || []).push({});

The first observation in this problem is that both T1 and T2 are unknowns since the weights are accelerating. Noting that the rope is taken to be inextensible, we get the eq's of constraint I have written below which allow for a relation between Aa and Ab to be derived as well as for Ab and Ac. I believe these to be correct as they are fairly simple.

Anyways if I solve the system at the end using a scrap peice of paper OR my calulator (tried both ways to make sure) I get Ab = -4.6ft/s^2, and according to my arbitrary selection of direction for Ab, this means 4.6ft/s^2 downward. Anyways, the solution in the book is 2.48ft/s^2 UPWARDS. I have spent a long long time checking my math, so I suppose I will admit that there must be a flaw in my technique unless the answer in the back is wrong.

I would appreciate it dearly if anyone would help me with this problem!

1. The problem statement, all variables and given/known data

http://img227.imageshack.us/img227/5333/3491219pm6.jpg [Broken]

Specifically question 12.19

2. Relevant equations

F=mA Ma=Wa/g

3. The attempt at a solution

http://img228.imageshack.us/img228/4917/349prob004yc2.jpg [Broken]

http://img227.imageshack.us/img227/9090/349prob005bc6.jpg [Broken]

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# Homework Help: Kinetics Question (Dependant motion, gravity, pulleys)

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