Supose a car, going at a constant velocity

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SUMMARY

The discussion centers on the types of friction involved when a car decelerates and when it navigates a circular curve. It is established that static friction is responsible for stopping the car when brakes are applied, despite the car's motion, because the point of contact between the tire and the road does not slide. Similarly, when a car turns, static friction accelerates it towards the center of the curve, as the tires maintain static contact with the road surface. Kinetic friction is present in the brake pads but does not apply to the tire-road interaction during these scenarios.

PREREQUISITES
  • Understanding of basic physics concepts, particularly friction.
  • Familiarity with the mechanics of vehicle motion.
  • Knowledge of the differences between static and kinetic friction.
  • Awareness of rolling resistance principles.
NEXT STEPS
  • Research the principles of static vs. kinetic friction in detail.
  • Study the mechanics of vehicle dynamics, focusing on tire-road interactions.
  • Explore the concept of rolling resistance and its impact on vehicle performance.
  • Investigate the role of friction in various driving scenarios, including braking and cornering.
USEFUL FOR

Physics students, automotive engineers, driving instructors, and anyone interested in understanding vehicle dynamics and the role of friction in motion.

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1. Supose a car, going at a constant velocity, decelerates to a stop by pressing the brakes. Is the friction used to stop the car kinetic or static friction? PLEASE explain why. My teacher said the answer was static friction, but I don't understand this. Since the car is already moving and the surface of the wheel is sliding past the ground, isn't kinetic friction causing the car to come to a stop.

2. When a car is going around a circular curve, is the friction used to accelerate the car towards the center of the curve static or kinetic friction. Again, my teacher said the answer was static friction, but I don't understand this. Since the car is already moving and the surface of the wheel is sliding past the ground, isn't kinetic friction causing the car to accelerate towards the center?
 
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Is the bottom of the tire sliding on the roadway? That would be kinetic friction.

If you carefully consider the motion of the tire you will find that at the point of contact ("where the rubber meets the road") the tire and the roadway are in static contact.

The brake pads are subject to kinetic friction.

"Rolling resistance" or "rolling friction" would be a better term than static friction; see
http://en.wikipedia.org/wiki/Rolling_resistance
 

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