Understanding the Movement of a Sphere on a Frictionless Surface

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Discussion Overview

The discussion revolves around the movement of a sphere on a frictionless surface when a force is applied to a string attached to the top of the sphere. Participants explore the implications of this setup regarding torque, rotational movement, and translational movement.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • Some participants propose that applying a force to the string will create torque if the force does not pass through the center of mass.
  • Others argue that the scenario is similar to a sphere floating in space, suggesting that rotation will occur due to the applied force.
  • There is a question about whether translational movement will also occur alongside rotation when the force is applied.
  • Some participants assert that the force acting on the center of mass is equivalent to the force applied at the top of the sphere.

Areas of Agreement / Disagreement

Participants generally agree that applying a force will result in both rotational and translational movement, but the specifics of how these movements relate to each other remain somewhat unclear.

Contextual Notes

There are unresolved questions regarding the exact relationship between the force applied at the top of the sphere and the resulting forces acting on the center of mass.

mbrown3391
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Imagine a sphere on a frictionless surface. A string is attached to the top of the sphere, as shown. If a force is applied to the string, how will the sphere move? Will there be any torque at all, even though there is no friction? Or will the sphere move in exactly the same way as if the string was attached to the side of the sphere?
 
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mbrown3391 said:
Will there be any torque at all, even though there is no friction?
Sure. Your scenario is equivalent to a sphere floating in space. If the force doesn't go through the center of mass, it will start rotating.
 
Ok, that's what i figured. But will there be translational movement as well? If so, how can you describe the force that acts on the center of mass as a function of the force that acts at the top of the sphere?
 
mbrown3391 said:
But will there be translational movement as well?
Yes
mbrown3391 said:
If so, how can you describe the force that acts on the center of mass as a function of the force that acts at the top of the sphere?
They are the same
 
Ok, thanks for you help!
 

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