Rotational Dynamics problem with instantaneous frame of reference

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Homework Help Overview

The discussion revolves around a rotational dynamics problem involving instantaneous frames of reference. Participants are exploring the nature of the problem and the correct approach to solving it, particularly in relation to the velocities of points in a rotating system.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are discussing the need for a clear strategy before applying equations. There are questions about the setup of the problem, including the positions and velocities of points A and B. Some participants suggest describing the approach in words before presenting equations.

Discussion Status

The discussion is ongoing, with participants providing feedback and requesting clarification on the original poster's approach. There is an emphasis on understanding the problem rather than simply checking work, and some guidance has been offered regarding the need for clarity in communication.

Contextual Notes

There are indications that the original poster is aware of errors in their solution and is seeking guidance for future problems. The format of the original post has been criticized for being unclear, which may affect the discussion.

YK0001
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Homework Statement
The wheel rolls without slipping such that at the instance shown, it has the angular velocity ##\omega## and angular acceleration ##\alpha##. Determine the velocity and acceleration of point B on the rod at this instant. [![The image that shows the frame][1]]

[1[https://imgur.com/a/zRjzbDA]]
Relevant Equations
$$
v_B = v_A + \omega_{BA} \times r_{B/A}\newline ~~~
v_A = \omega r_{A/IC}\newline ~~~
a_B = a_A + \alpha_{BA} \times r_{B/A} + \omega \times (\omega \times r_{B/A})
$$
20241004_181812.jpg
20241004_181820.jpg
 
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Is there a question in there somewhere? Are we supposed to check your work?

When you ask someone for a favor, such as checking your work, it is exceptionally bad form to make it hard for them by posting your work sideways and in sloppily hand written form.

Just sayin'.
 
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phinds said:
Is there a question in there somewhere? Are we supposed to check your work?

When you ask someone for a favor, such as checking your work, it is exceptionally bad form to make it hard for them by posting your work sideways and in sloppily hand written form.

Just sayin'.
Hi phinds,

Thank you for your response. I appreciate your feedback. I apologize if my post was unclear. I am not asking for someone to check my work for errors. I am aware that my solution is incorrect because it does not match the answer key. I am simply requesting guidance on how to solve this type of problem so that I can understand the correct approach for similar problems in the future.

Thank you for your understanding.
 
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YK0001 said:
I am simply requesting guidance on how to solve this type of problem so that I can understand the correct approach for similar problems in the future.
Before writing down any equations you need a strategy. It is very difficult to understand your strategy, which you say gave the wrong answer, from what you have posted. It may be that you have the correct approach but you went astray somewhere along its implementation. So how about describing with words how you propose to approach this problem? Then provide any equation that you may think is relevant to this strategy. When you do that, please show some consideration to those who are trying to help you and proofread your reply before posting it. Do not show equations that are cut in half or pictures that are sideways.
 
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Welcome. @YK0001 !

Consider that point A has an instantaneous velocity that can be considered as two components: one horizontal (same as velocity of point O) and another vertical (tangential).
Consider that point B has an instantaneous velocity which direction is constrained to be only horizontal.
Therefore, the A-B link is simultaneously experimenting a rotation and a translation respect to the ground.

Rolling wheel 3.jpg


Rolling wheel 1.jpg
Rolling wheel 2.jpg
 
Last edited:
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I have been working with @YK0001 on LaTeX, so hopefully any follow-up posts by them should use LaTeX.
 
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Question to OP:
When is "this instant"? In the figure it appears that point A is at the 9 o'clock position. Is that correct?
 

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