Car moving at constant velocity.

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Discussion Overview

The discussion revolves around the forces acting on a car moving at constant velocity, particularly focusing on the role of friction and other resistive forces. Participants explore the balance of forces that allows for constant velocity, including various types of resistance encountered by the vehicle.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that friction is the force that accelerates cars, but question what force retards the car's motion when moving at constant velocity.
  • Others argue that in addition to wind resistance, mechanical drag, hysteresis of the tires, and other factors contribute to the resistance that must be overcome for constant velocity.
  • A participant mentions the role of gravity and various mechanical components, suggesting that multiple forces are at play in the car's motion.
  • Rolling resistance and aerodynamic drag are identified as specific forces acting to retard the car's motion, distinct from static friction.

Areas of Agreement / Disagreement

Participants generally agree that multiple forces act to retard the car's motion, but there is no consensus on the primary factors or the completeness of the explanations provided.

Contextual Notes

Some participants express uncertainty about their understanding of the concepts, and there may be missing assumptions regarding the definitions of forces involved in the discussion.

siddharth5129
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As I understand it, friction is the force that accelerates cars on a road. Assuming that the car moves at a constant velocity, there is no net force on the car. But in this case, if friction acts to accelerate the car, what force acts to retard the car's motion? Surely it can't be purely the wind resistance as that would depend solely on the vehicles speed, and would not necessarily cancel out the forward fricitional force.
 
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siddharth5129 said:
As I understand it, friction is the force that accelerates cars on a road. Assuming that the car moves at a constant velocity, there is no net force on the car. But in this case, if friction acts to accelerate the car, what force acts to retard the car's motion? Surely it can't be purely the wind resistance as that would depend solely on the vehicles speed, and would not necessarily cancel out the forward fricitional force.

The resistance in addition to wind would be mechanical drag, hysteresis of the tires, and so forth.

In other words, the car has to overcome the resistance of the drive train rotation, meshing gears, spinning a flywheel up to speed, rolling resistance of the tires, brake drag, mechanical losses to drive accessory belts, etc.
 
I most probely am reading your question wrong, also I am not a Physicist. Other than the Air.

The rubber wheels on the tarmac, bearings and all the other moving parts on the car, then you have gravity.

Wayne
 
siddharth5129 said:
What force acts to retard the car's motion?
Rolling resistance (which is different than static friction) and aerodyanmic drag. Wiki article for rolling resistance:

http://en.wikipedia.org/wiki/Rolling_resistance
 
rcgldr said:
Rolling resistance (which is different than static friction) and aerodyanmic drag.
Thanks. That really cleared it out for me.
 

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