Why Does Friction Provide Centripetal Acceleration in Circular Motion?

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Discussion Overview

The discussion revolves around the role of friction in providing centripetal acceleration for objects in circular motion. Participants explore the forces acting on a particle moving along a circular path, questioning how friction contributes to maintaining circular motion and the nature of static versus kinetic friction in this context.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that friction is necessary to provide centripetal acceleration, analyzing the forces acting on a particle in circular motion.
  • Another participant challenges the idea that static friction is always directed opposite to the velocity, arguing that static friction can act in any direction depending on the interaction between surfaces.
  • Concerns are raised about the application of Newton's laws in the context of circular motion, with some participants questioning the validity of earlier statements regarding friction's role.
  • A participant emphasizes that the geometry of the trajectory and the reactive forces from the surface are crucial for understanding changes in direction, suggesting that friction is not the sole factor.
  • Discussion includes the distinction between static and kinetic friction, with participants noting that static friction adjusts to prevent relative motion while kinetic friction acts opposite to the direction of motion.
  • Some participants express confusion over the mechanics of friction during circular motion, particularly how it relates to acceleration and the forces involved.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the role of friction in providing centripetal acceleration. Multiple competing views are presented regarding the nature of friction and its interaction with motion, leading to an unresolved discussion.

Contextual Notes

Participants highlight limitations in their explanations, including the need for specific mechanisms of friction and the conditions under which different types of friction apply. The discussion remains open-ended with various assumptions and interpretations of friction's role in circular motion.

Who May Find This Useful

This discussion may be of interest to students and enthusiasts of physics, particularly those exploring concepts of motion, forces, and friction in circular dynamics.

  • #31
Vigorous said:
When I turn the wheels, ...
How the particle moving around a circular track described in post #1 ended up having wheels and a steering mechanism? :smile:

Please, see:
https://en.m.wikipedia.org/wiki/Camber_thrust
 
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  • #32
Vigorous said:
I can't grasp how from this friction will act radially inwards?
What static friction opposes is the relative motion at contact that would occur if there was no friction (marked red in the diagram).

wheel_relative_motion_hs.png
 
  • #33
Lnewqban said:
How the particle moving around a circular track described in post #1 ended up having wheels and a steering mechanism? :smile:

See post #3:
Vigorous said:
but why and how does friction cause a car to turn?
 
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  • #34
Vigorous said:
Picture a runner in the right direction, let the runner plant his left foot on the floor, he is exerting a force down and backward on the floor, the left leg stays in contact with the floor for a few milliseconds, and the right leg is in mid air, after those milliseconds, the force exerted exceeds the maximum limit of static friction and slippage occurs. By Newtons third law, the ground exerts an equal and opposite force on the runner but do we identify this force as static or kinetic friction
You seem to be confused that friction is a reaction force to the force you apply to move any object. In fact it is not. It is a force that occurs due to electromagnetic interaction between the 2 surfaces in relative motion. In fact if you were to take an object to outer space and push it, it is not friction that is reacting to your push (because action reaction pair always act on different bodies) it the push of the object on you. You can see that you will be pushed backwards when you try to push the object forward in space. This can be recreated by standing on a roller skate and trying to push the wall, you seem to go backward even though you push the wall forward, this is the reaction force that the wall exerts on you when you exert a force on the wall.
 
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  • #35
As I turn the wheels to the left the wheels are pushing to the right against the floor. Friction allows the floor to push back against the wheels allowing them to turn left. If there was no friction then the object would fly off the circular trajectory and continue in the direction of the tangential velocity.
 
  • #36
Vigorous said:
If there was no friction then the object would fly off the circular trajectory and continue in the direction of the tangential velocity.
Yes. the car would move tangentially. But the relative motion between road and the bottom of the rotating wheel would radial (red arrow below). If present, static friction opposes that motion, and acts radially, thus providing a centripetal force to the car.

wheel_relative_motion_hs-png.png
 
  • #37
Vigorous said:
As I turn the wheels to the left the wheels are pushing to the right against the floor. Friction allows the floor to push back against the wheels allowing them to turn left. If there was no friction then the object would fly off the circular trajectory and continue in the direction of the tangential velocity.
Yes you got it right
 
  • #38
Vigorous said:
... If there was no friction then the object center of mass of the object would fly off the circular trajectory and continue in the direction of the tangential velocity.

... the center of mass of the object.

giphy%2B%252816%2529.gif
 

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