Rotational Motion Homework: K1+U1=K2+U2

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Homework Help Overview

The discussion revolves around a problem related to rotational motion, specifically analyzing the energy conservation equation K1 + U1 = K2 + U2 in the context of a cylinder on a tabletop. Participants are examining the conditions under which the cylinder rotates and translates, particularly focusing on the implications of friction and the attachment of the string.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning whether the cylinder should have both translational and rotational kinetic energy given the frictionless nature of the table and the attachment of the string at its center. There is a discussion about the implications of the cylinder rolling without slipping and what that means for the energy types involved.

Discussion Status

There is an active exploration of the assumptions regarding friction and motion. Some participants suggest that the cylinder's rolling condition indicates that it does indeed have rotational motion, while others are clarifying the definitions and conditions stated in the problem. No consensus has been reached yet.

Contextual Notes

Participants are navigating the implications of the problem's conditions, particularly the frictionless tabletop and the rolling without slipping condition, which may affect the interpretation of kinetic energy types involved.

Muath Mushtaha
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Homework Statement


http://serv1.gulfup.cc/i/00003/ev7u8r04c18k.jpg

Homework Equations


K1+U1=K2+U2

The Attempt at a Solution


I have the solution i am just confused about one point,
in the solution, it considred both the translational and rotational kinetic energy for the cylinder on the tabletop,
but since the table is frictionless and the string is attached to its center, shouldn't it not rotate, thus only have translational energy and not rotational energy?
 
Last edited by a moderator:
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Muath Mushtaha said:

Homework Statement


http://serv1.gulfup.cc/i/00003/ev7u8r04c18k.jpg

Homework Equations


K1+U1=K2+U2

The Attempt at a Solution


I have the solution i am just confused about one point,
in the solution, it considred both the translational and rotational kinetic energy for the cylinder on the tabletop,
but since the table is frictionless and the string is attached to its center, shouldn't it not rotate, thus only have translational energy and not rotational energy?
The problem states that the cylinder rolls without slipping. That means that the table surface is not frictionless.
 
Last edited by a moderator:
It clearly states that the cylinder does not slip, essentially the distance traveled is only by rolling. So just consider the rotational motion.
 
Frictionless are mechanical parts.
 

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