Direction of Friction in Rolling Objects

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SUMMARY

The discussion centers on the direction of friction for a rolling wheel under a forward force applied at the axle on a horizontal surface. Participants debate whether the frictional force acts forward or backward, with conflicting interpretations from textbooks and answer keys. The consensus is that when a forward force accelerates the wheel, the frictional force acts backward, opposing the direction of motion. This conclusion aligns with Newton's third law, where the surface exerts a backward force on the wheel.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with static friction and its role in rolling motion
  • Basic knowledge of torque and angular acceleration
  • Ability to interpret free body diagrams
NEXT STEPS
  • Study the relationship between linear acceleration and angular acceleration in rolling objects
  • Learn about free body diagrams and how to analyze forces acting on rolling bodies
  • Investigate the effects of different surfaces on frictional forces in rolling motion
  • Explore the application of Newton's third law in various mechanical systems
USEFUL FOR

Physics students, educators, and anyone interested in understanding the mechanics of rolling motion and frictional forces in real-world applications.

  • #31
I have a question that seems to best fit into this thread.

I'm only concerned with the direction of friction. I believe that as you accelerate down the road the fs is forward for the wheels subjected to torque and backwards for the wheels being 'pushed'. If i have that right then my question is when the brakes are applied and assuming there is not any slipping (the car gradually slows down) are the forces of friction switched? Meaning, do the tires under torsion have a frictional force opposing the velocity of the vehicle?
 
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  • #32
The directions of the forces associated with friction between a pair of surfaces always acts to reduce the relative motion between the two surfaces. To apply this to a situation where there is no slip imagine the motion that would take place if friction between the two surfaces was zero.
 
  • #33
Nyhm said:
I have a question that seems to best fit into this thread.

I'm only concerned with the direction of friction. I believe that as you accelerate down the road the fs is forward for the wheels subjected to torque and backwards for the wheels being 'pushed'. If i have that right then my question is when the brakes are applied and assuming there is not any slipping (the car gradually slows down) are the forces of friction switched? Meaning, do the tires under torsion have a frictional force opposing the velocity of the vehicle?
Yes, you are correct.
 

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