Solving 2 Rotating Discs Homework: Angular Velocities

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SUMMARY

The forum discussion centers on solving a physics homework problem involving two discs with different radii and angular velocities. The larger disc has an initial angular velocity ω, while the smaller disc has a radius half that of the larger. The participants derive the angular velocities of both discs using the equations for rotational motion and conservation of angular momentum, ultimately concluding that ω1 = ω/√5 and ω2 = ω/(2√5). The discussion highlights the importance of correctly applying the principles of angular momentum and torque in rotational dynamics.

PREREQUISITES
  • Understanding of rotational dynamics and angular velocity
  • Familiarity with the equations of motion for rotating bodies, specifically the moment of inertia
  • Knowledge of conservation laws in physics, particularly angular momentum
  • Ability to manipulate algebraic equations involving variables and constants
NEXT STEPS
  • Study the principles of conservation of angular momentum in non-isolated systems
  • Learn about the relationship between torque and angular acceleration
  • Explore the derivation of moment of inertia for various shapes, including discs
  • Investigate the effects of friction on rotational motion and energy transfer
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Students studying physics, particularly those focusing on mechanics and rotational dynamics, as well as educators looking for examples of angular momentum problems and solutions.

  • #31
person123 said:
Alright. I finally think I have the answer... They both follow the format of ##IΔω=F_{f}rt## . I divided one by the other, leaving me with:

##\frac {r_{2}^4(ω_{2}-ω_{1})} {r_{1}^4ω_{1}}=-\frac {r_{2}} {r_{1}}##

. When simplifying and substituting the values for r1 and r2, it gave me:

##ω_{2}=\frac {ωr_{2}^2} {r_{1}^2+r_{2}^2}##
##ω_{1}=\frac {r_{2}^3ω} {r_{1}^3+r_{1}r_{2}^2}##
I arrived at the same answer, which I posted on his YouTube video, this morning. As of 3:30 PM central time today, he has not released it to the public view. So I'm going to assume it is probably correct.
 
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  • #32
scottdave said:
I arrived at the same answer, which I posted on his YouTube video, this morning. As of 3:30 PM central time today, he has not released it to the public view. So I'm going to assume it is probably correct.
:smile: At last! I'm just going to wait a while to make sure I got it, and then I'll close the thread.
 
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