Rotational Motion Question

1. Oct 9, 2011

GreenPrint

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

Please see the attachment.

2. Relevant equations

3. The attempt at a solution

Please see the attachment. When I tried to solve the equations for a I got a different answer and I don't see what I'm doing wrong. Please let me know if you cannot follow my work. Thanks for any help you can provide.

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2. Oct 9, 2011

SammyS

Staff Emeritus
Illegal algebra cancellation.

$$\frac{MR^2}{2}\frac{a}{r}=(F_T)\,r$$

In the above equation, you cancelled r on the left side with r on the right side.

3. Oct 9, 2011

GreenPrint

oh that's embarrassing thanks

4. Oct 9, 2011

WJSwanson

Don't be embarrassed by it. Arithmetic and algebraic mistakes just plumb happen even to the best of us. I've had a professor who was the chair of my university's physics department and who performs nuclear physics experiments (specifically with lead nuclei, IIRC) at the LHC, and on occasion he made algebra errors when demonstrating examples on the board. Just go through stuff more slowly and carefully, and you should minimize the number of those mistakes that you make. :)