Why is friction acting in the tangential direction?

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Homework Help Overview

The discussion revolves around the behavior of friction in relation to a turntable experiencing angular acceleration. Participants are exploring the direction of the frictional force in the context of a rotating system.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the direction of the frictional force, particularly why it is acting tangentially rather than opposing the motion. There are inquiries about the conditions of the turntable, including its angular acceleration and the implications for friction.

Discussion Status

Some participants have provided insights regarding the angular acceleration of the turntable and its effect on friction. There is an ongoing exploration of the components of friction and tension, with no clear consensus reached yet.

Contextual Notes

Participants mention specific values such as the maximum tension the cord can sustain and the coefficient of static friction, indicating constraints that may influence the discussion.

eurekameh
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eurekameh said:
http://imageshack.us/photo/my-images/440/49789320.png/
Assuming the indicated direction of motion, why is friction acting as shown in the tangential direction? Shouldn't it be acting in the opposite direction?
Is there some information you're not letting us in on? For instance, is the turntable undergoing negative angular acceleration?
 
The turntable is actually undergoing positive angular acceleration with its motion shown counter-clockwise.
We're looking for the time it takes for the turntable to reach a speed great enough to break the cord, which can only sustain a maximum tension of 100 N. mu,s = 0.1 and the mass of the disk D is 3 kg.
 
Then friction must have a tangential component as well as a radial component as shown in the figure.
 
Friction only has a tangential component as shown in the figure. The T in the radial component is the tension in the string. My question is: why is the friction force acting in the positive tangential direction, if friction opposes motion?
 
Bump.
 

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