Why Is My Solution for Rotational Motion Incorrect?

[GreenPrint]

Homework Statement

Please see the attachment.

Homework Equations

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.

 

[SammyS]

Illegal algebra cancellation.

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

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

 

[GreenPrint]

oh that's embarrassing thanks

 

[WJSwanson]

oh that's embarrassing thanks

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. :)

 

[rwisz]

It would be helpful if you could provide more information about the specific question and equations involved. Without this information, it is difficult for me to provide a meaningful response. However, I can offer some general advice for approaching rotational motion problems.

First, make sure you understand the physical concepts involved in the problem, such as torque, angular velocity, and moment of inertia. Next, carefully read the problem and identify the given information and what you are trying to solve for. Then, use the appropriate equations and principles to set up your solution. It is important to be consistent with units and to double check your calculations.

If you are still having trouble, I suggest seeking help from your teacher or a tutor who can provide personalized guidance. Additionally, there are many online resources and textbooks available that can provide examples and practice problems to help you improve your understanding of rotational motion. Keep practicing and don't get discouraged, as mastering this topic takes time and effort.