Direction of Friction in Rolling Objects

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The discussion revolves around the direction of friction acting on a rolling wheel when a forward force is applied at the axle on a horizontal surface. Participants debate whether the frictional force is zero, forward, backward, or vertical, with some referencing textbook diagrams that suggest conflicting answers. The consensus leans towards the frictional force acting backward, opposing the direction of the applied force, as it is necessary to prevent slipping and provide the required torque for the wheel's rotation. The conversation highlights the importance of distinguishing between applied forces and torques in analyzing rolling motion. Overall, the frictional force in this scenario is confirmed to act in the backward direction relative to the applied forward force.
  • #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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