Why Is the Angular Velocity of a Clockwise-Spinning CD in the -y Direction?

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SUMMARY

The angular velocity of a clockwise-spinning CD, when viewed from above, is definitively in the -y direction. This conclusion is derived from applying the right-hand rule, where the thumb points in the direction of the angular velocity vector. The confusion arises from the interpretation of the rotation axis; when considering the vertical y-axis as the axis of rotation, the angular velocity vector points downward, confirming the -y direction. This analysis clarifies the dimensional considerations involved in determining angular velocity.

PREREQUISITES
  • Understanding of angular velocity and its vector representation
  • Familiarity with the right-hand rule for determining rotational direction
  • Basic knowledge of coordinate systems in physics
  • Concept of rotational motion in two dimensions
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  • Study the right-hand rule in detail for various rotational scenarios
  • Explore angular momentum and its relationship with angular velocity
  • Investigate the effects of different axes of rotation on angular velocity
  • Learn about rotational dynamics and its applications in real-world systems
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Students studying physics, particularly those focusing on rotational motion, as well as educators looking for clear explanations of angular velocity concepts.

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Homework Statement


A CD player spins a disc in a clockwise direction when looking at the player from the top. What is the direction of the angular velocity.


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The Attempt at a Solution


OK, the key for this practice exam says the answer is in the -y direction. I used the right hand rule to see that the direction is negative, but I thought it would be in the -z direction. Can someone explain why it is -y?
 
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I believe they have made the answer this way as you are only using two dimensions. If you take the vertical y-axis as the axle for the rotation, your right thumb will be pointing in the negative y-direction when you use the right hand rule.
 

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