Determine the angular velocity as a function of the angle

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Homework Help Overview

The problem involves determining the angular velocity of a solid body that begins to rotate around a fixed axis with a specified angular acceleration that varies with the angle of rotation. The context is within the subject area of rotational dynamics and circular motion.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between angular acceleration and angular velocity, exploring the use of calculus, particularly integration, to find the angular velocity as a function of the angle. There are questions about the application of the chain rule and the interpretation of hints provided regarding the relationships between variables.

Discussion Status

The discussion is ongoing, with participants attempting to clarify their understanding of the integration process and the implications of initial conditions. Some have suggested using conservation principles, while others are exploring the correct formulation of the equations involved.

Contextual Notes

Participants note the absence of explicit initial conditions, leading to discussions about how to determine constants of integration based on the problem statement. The initial condition that the body begins to rotate from rest is highlighted as significant for determining the constant of integration.

  • #31
Davidllerenav said:
Ok, So it would be ##\frac{\omega^2}{2} = \beta_0 \sin\varphi+0##, right? I understand, thanks! How do I draw the graph of the dependence?
It just means sketch a graph of ω against φ.
 
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  • #32
haruspex said:
It just means sketch a graph of ω against φ.
But how to I graph that?
 
  • #33
Davidllerenav said:
But how to I graph that?
How do you sketch any graph?
Pick a few convenient values of x and see what y is.
Same for gradients at the same points.
Consider local extrema and asymptotic behaviour.
 
  • #34
haruspex said:
How do you sketch any graph?
Pick a few convenient values of x and see what y is.
Same for gradients at the same points.
Consider local extrema and asymptotic behaviour.
But there isn't any x or y. It is polar coordinates, right?
 
  • #35
Davidllerenav said:
But there isn't any x or y. It is polar coordinates, right?
You are just sketching a graph of one variable against another. The physical meanings are irrelevant.
You could sketch it in polar if you wish, but I doubt that is what is expected.
 
  • #36
haruspex said:
You are just sketching a graph of one variable against another. The physical meanings are irrelevant.
You could sketch it in polar if you wish, but I doubt that is what is expected.
So I have to set ##\omega## as y and ##\varphi## as x, right? Then I you said I just need to plug in values. The values that would be easy to cumpute would be ##\varphi=0##, ##\varphi=1##, ##\varphi=\pi##, ##\varphi=\pi/2##, right?
 
  • #37
Davidllerenav said:
But there isn't any x or y. It is polar coordinates, right?
To plot angular velocity, ##\omega ,## as a function of ##\varphi##, the usual convention is to plot ##\varphi## on the x-axis and angular velocity, ##\omega ,## on the y-axis.
 
  • #38
SammyS said:
To plot angular velocity, ##\omega ,## as a function of ##\varphi##, the usual convention is to plot ##\varphi## on the x-axis and angular velocity, ##\omega ,## on the y-axis.
Like I said on post #36?
 
  • #39
Davidllerenav said:
Like I said on post #36?
Well, yes for:
Davidllerenav said:
So I have to set ##\omega## as y and ##\varphi## as x, right?

However, the following isn't quite right.
The values that would be easy to cumpute would be ##\varphi=0##, ##\varphi=1##, ##\varphi=\pi##, ##\varphi=\pi/2##, right?
At least, ## \varphi=1## is not an easy value, is it?

Other values "easy" for ##\varphi## are ##\dfrac{\pi}{6} ## and ##\dfrac{5\pi}{6} ##.
 
  • #40
SammyS said:
At least, ## \varphi=1## is not an easy value, is it?
Oh, yes it isn't, sorry.
SammyS said:
Other values "easy" for φφ\varphi are π6π6\dfrac{\pi}{6} and 5π65π6\dfrac{5\pi}{6} .
Yes, you're right.
 

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