Determine the angular velocity as a function of the angle

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SUMMARY

The discussion focuses on determining the angular velocity (##\omega##) of a solid body rotating around a fixed axis with angular acceleration defined as ##\beta = \beta_0 \cos \varphi##. The solution involves using calculus, specifically integrating the relationship between angular acceleration and angular velocity, leading to the equation ##\frac{\omega^2}{2} = \beta_0 \sin \varphi##. The constant of integration is determined using initial conditions, concluding that when ##\varphi = 0##, ##\omega = 0##. Participants also discuss graphing this relationship, suggesting plotting ##\varphi## on the x-axis and ##\omega## on the y-axis.

PREREQUISITES
  • Understanding of angular motion and angular acceleration
  • Familiarity with calculus, particularly integration
  • Knowledge of the Chain Rule in calculus
  • Basic concepts of graphing functions
NEXT STEPS
  • Study the principles of angular motion and related equations
  • Learn how to apply integration techniques in physics problems
  • Explore the Chain Rule and its applications in motion equations
  • Practice graphing functions, particularly in polar coordinates
USEFUL FOR

Students studying physics, particularly those focusing on rotational dynamics, as well as educators teaching calculus applications in motion. This discussion is also beneficial for anyone looking to enhance their problem-solving skills in mechanics.

  • #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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