Rotational motion of a solid sphere of mass

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Discussion Overview

The discussion revolves around the dynamics of a solid sphere of mass m rolling inside a hemispherical cup. Participants explore the normal force exerted by the cup on the sphere when it reaches the bottom, considering the orientation of the cup's rim and bottom.

Discussion Character

  • Homework-related, Technical explanation

Main Points Raised

  • One participant states that the normal force at the bottom of the cup must equal the weight of the ball, suggesting it acts upwards with a magnitude of m*g.
  • Another participant clarifies that the rim of the cup is horizontal, which is a point of contention regarding the orientation of the cup.
  • A further participant questions whether the tangent plane to the bottom of the cup is indeed horizontal, indicating a potential misunderstanding or need for clarification.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of the cup's orientation and how it affects the normal force calculation. Multiple viewpoints are presented without resolution.

Contextual Notes

There is ambiguity regarding the definitions of the cup's rim and bottom orientations, which may affect the interpretation of the normal force. The discussion does not resolve these definitions.

kaka01
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A solid sphere of mass m is released from rest from the rim of a hemispherical cup so that it rolls along the surface. If the rim of the hemisphere is kept horizontal, find the normal force exerted by the cup on the ball when the ball reaches the bottom of the cup.
 
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This sounds suspiciously like a homework question... anyway, the bottom of the cup is horizontal so the normal force must be equal and opposite to the weight of the ball, ie. acting upwards and of magnitude m*g.
 
MikeyW said:
This sounds suspiciously like a homework question...
Yep. It belongs in the Intro Physics forum.
anyway, the bottom of the cup is horizontal
No, the rim of the cup is kept horizontal.
 
Last edited:
Okay, so the tangent plane to the bottom of the cup is horizontal?
 

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