Find average velocity of a sphere which expands and moves

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SUMMARY

The discussion focuses on calculating the average velocity of a spherical shell that expands and moves, specifically addressing the velocities involved: expansion velocity (v) and movement velocity (v'). Participants clarify that while expansion velocities can cancel out in certain contexts, the average velocity remains dependent on the movement velocity v'. The kinetic energy of the shell is also discussed, emphasizing that energy is a scalar quantity and does not simply cancel out like vector quantities. The conversation highlights the need for proper mathematical treatment, including the use of double integrals in spherical coordinates for accurate calculations.

PREREQUISITES
  • Understanding of vector and scalar quantities in physics
  • Familiarity with kinetic energy concepts and equations
  • Knowledge of spherical coordinates and double integrals
  • Basic principles of symmetry in physics problems
NEXT STEPS
  • Study the derivation of kinetic energy in spherical coordinates
  • Learn about the application of double integrals in physics problems
  • Explore the concept of center of mass and its implications in motion
  • Review vector addition and cancellation in the context of physics
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and energy concepts, as well as educators looking for examples of complex motion and energy calculations involving spherical objects.

  • #91
Quarlep said:
Can dtheta and dphi change sides
Do you mean, can they be in either order? Yes. It's the order of the integral signs that defines the order of integration (inside first).
 
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  • #92
I am in holiday I am not working in computer so I can't write all steps to you right now.We will do first integral (the one which is inside) that's phi but there wrote dtheta so I asked you this
 
  • #93
Can you tell me what was that please the only thing I ll do is put it on program
 
  • #94
Quarlep said:
Can you tell me what was that please the only thing I ll do is put it on program
Sorry, I don't understand what you are asking.
 
  • #95
The answer :):)
 
  • #96
Quarlep said:
The answer :):)
Do you simply want the answer to the original question, by whatever means, or do you specifically want to see how to do it through an elaborate double integral?
 
  • #97
I want to see answer to the original question
 
  • #98
I am working on symbolab but I found nothing
 
  • #99
Quarlep said:
I want to see answer to the original question
Then use my symmetry method. It gets rid of the trig terms and makes the integral trivial.
 
  • #100
I was banned so I couldn't answer over a 10 days I found 4p(pi)r^2((v'^2)+v^2)
 
  • #101
Quarlep said:
I was banned so I couldn't answer over a 10 days I found 4p(pi)r^2((v'^2)+v^2)
I think it should be exactly half that.
Note that the factor outside the parentheses is just the mass.
 
  • #102
Thank you so much. Problem is solved now.
 

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