Direction of Friction for Rolling Spheres on Rough Surfaces

In summary, the direction of friction in a case of a smooth spherical body pure rolling on a rough surface depends on the initial situation. In most cases, if the ball is sliding over the surface, the backwards friction will cause it to transition to rolling without slipping. However, if the ball is spinning rapidly before hitting the surface, the forward friction will accelerate its motion and adjust the rate of rotation until there is no more slipping. It is also possible to have pure rolling without friction, as long as the condition v = ωR (speed = angular speed times radius) is met. This can be achieved by setting up the scenario with an external force. Ultimately, whenever an object is rolling without slipping at a constant speed, the friction force
  • #1
SDewan
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Hi all,
Can anyone please help me out with the direction of friction in a case where there is a smooth spherical body pure rolling on a rough surface? What is the direction of friction?
Also, is it possible to have pure rolling without friction?

Thanks
SD
 
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  • #3
Depends on the inital situation. Most frequent case: if a ball is sliding over a surface, the backwards friction will make it change over to rolling without slipping.

But if it hits the ground spinning like crazy (around a horizontal axis), the forward acting friction will accelerate the motion while adjusting the rate of rotation until there is no more slipping.

And yes: pure rolling without friction is possible. All that is required is ##v = \omega R ## (speed = angular speed times radius)[edit] sorry, missed the 'pure' as in pure rolling (meaning rolling without slipping). Agree with Russ #5.
 
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  • #4
SDewan said:
Also, is it possible to have pure rolling without friction?
You can always potential run into trouble if you work with models that are a mixture of ideal and practical. If you have 'no friction' then your model is very limited. You have to work with a very low value of friction - not zero.
BvU said:
And yes: pure rolling without friction is possible. All that is required is v=ωRv=ωRv = \omega R (speed = angular speed times radius)
You would need to set up that condition with some external force to produce the rolling.
 
  • #5
sophiecentaur said:
You can always potential run into trouble if you work with models that are a mixture of ideal and practical. If you have 'no friction' then your model is very limited. You have to work with a very low value of friction - not zero.

You would need to set up that condition with some external force to produce the rolling.
I think life is simpler: any time an object is rolling without slipping at constant speed, the friction force is zero - regardless of how it got to be that way.

If you want to quibble about exactness of such a scenario, roll a ball down a shallow incline. At some point it will reach a terminal velocity, where friction against the surface is exactly zero.
 
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  • #6
russ_watters said:
I think life is simpler: any time an object is rolling without slipping at constant speed, the friction force is zero - regardless of how it got to be that way.

If you want to quibble about exactness of such a scenario, roll a ball down a shallow incline. At some point it will reach a terminal velocity, where friction against the surface is exactly zero.
You're right . . . . . until you have to deal with yet another question on PF about it. :wink:
 
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What is the direction of friction for rolling spheres on rough surfaces?

The direction of friction for rolling spheres on rough surfaces depends on the direction of the motion of the sphere. If the sphere is rolling forward, the direction of friction will be in the opposite direction, slowing down the motion of the sphere. If the sphere is rolling backward, the direction of friction will be in the same direction, helping to maintain the motion of the sphere.

How does the roughness of the surface affect the direction of friction for rolling spheres?

The roughness of the surface plays a significant role in determining the direction of friction for rolling spheres. A rough surface will have more irregularities, creating more points of contact between the sphere and the surface. This results in a higher friction force, which will have a greater impact on the direction of the sphere's motion.

Can the direction of friction for rolling spheres on rough surfaces be changed?

Yes, the direction of friction for rolling spheres on rough surfaces can be changed by altering the direction of the sphere's motion or changing the roughness of the surface. For example, if the sphere is rolling forward, changing its direction of motion to rolling backward will result in the direction of friction changing as well.

What is the relationship between the coefficient of friction and the direction of friction for rolling spheres on rough surfaces?

The coefficient of friction is a measure of the amount of friction between two surfaces. The direction of friction for rolling spheres on rough surfaces is directly related to the coefficient of friction. A higher coefficient of friction will result in a greater direction of friction, and vice versa.

Can the direction of friction for rolling spheres on rough surfaces be calculated?

Yes, the direction of friction for rolling spheres on rough surfaces can be calculated using the equations of motion and the coefficient of friction between the sphere and the surface. However, the calculation may be more complicated due to the complexity of the rough surface and the varying points of contact between the sphere and the surface.

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