Centripetal acceleration question: car moving around banked curve

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Discussion Overview

The discussion revolves around the concept of centripetal acceleration in the context of a car moving around a banked curve, specifically focusing on the role of static friction and the conditions under which it applies. Participants explore the mechanics of tire contact with the road and the implications for frictional forces.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that when a car is turning on a banked curve without skidding, the force of friction is static friction, as the point of contact between the tire and the road does not move relative to the road.
  • Others clarify that while the point of contact is constantly changing as the tire rotates, it does not skid, thus static friction applies rather than kinetic friction.
  • One participant emphasizes that the coefficient of static friction indicates the maximum static friction force that can be transmitted, which may be less than the actual force experienced.
  • Another participant draws an analogy to walking, suggesting that while the feet do not move relative to the ground at the point of contact, forward motion is still possible through the switching of feet.

Areas of Agreement / Disagreement

Participants generally agree on the application of static friction when the car is not skidding; however, there is some disagreement regarding the implications of the coefficient of static friction and the nature of the forces involved.

Contextual Notes

Some participants express confusion regarding the explanation of static friction in this context, indicating a potential gap in understanding the mechanics involved. The discussion does not resolve these uncertainties.

Who May Find This Useful

This discussion may be of interest to individuals studying physics, particularly those focused on mechanics, as well as students seeking clarification on concepts related to friction and motion in vehicles.

gokuls
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If the wheels and tires of a car are rolling without slipping or sliding when turning, the bottom of the tire is rest against the road at each instant, so the force of friction is the static friction. Essentially if you are moving around a banked curve and the car is not skidding, then friction will be calculated by using coefficient of static friction. Why though? Isn't the car moving?
 
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The point of the tire in contact isn't moving- it is constantly changing as the tire rotates, but it is not skidding so it uses static rather than kinetic friction.
 
schaefera said:
The point of the tire in contact isn't moving- it is constantly changing as the tire rotates, but it is not skidding so it uses static rather than kinetic friction.

I still don't understand. Could you elaborate a bit more? Alright the car is not skidding, but I still don't understand.
 
Like schaefera said, you will use the static friction coefficient as the point of the tire in contact with road is not moving against the road. The wheels TURN and so the point in contact changes. Of course the previous point in contact moves but not against the road. So since the point is not moving but only changing its position that too not against the road, each point will have μ as the static friction co-efficient.
 
Last edited:
gokuls said:
Essentially if you are moving around a banked curve and the car is not skidding, then friction will be calculated by using coefficient of static friction.
Not quite, The coefficient of static friction just tells you what the maximal static friction force is, that the contact could transmit. The actual transmitted force of static friction can be less than that.

gokuls said:
Alright the car is not skidding, but I still don't understand.
No skidding = no relative horizontal movement between the contact patches. The tire contact point moves on a cycloid. Around contact time it moves only vertically:

http://en.wikipedia.org/wiki/Cycloid
 
Static friction occurs when there is no slipping between the surfaces. If the tyres don't slip, then this is what you use.
 
Compare it with walking: When your feet touch the surface, they do not move (relative to the surface), but you can move forward as you constantly switch between both feet.
 
mfb said:
Compare it with walking
bike-wheel-out-of-boots.jpg
 

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