Frictional Force: Motion Direction Example?

[oreo]

Is there an example in which friction acts in direction of motion. Any special case.

 

[Maged Saeed]

In Rolling motion , If you have a tire , the frictional force would oppose the tendency of the tire to slide back , that means the frictional force will act to the opposite direction to slide motion and in the direction of the translation motion of the tire,,

Hope it is obvious ,,

 

[oreo]

But we can apply this to every case
Actually in this case also the frictional force is opposing motion of tire. If it is true then the tire should accelerate by itself.

 

[Maged Saeed]

But we can apply this to every case
Actually in this case also the frictional force is opposing motion of tire. If it is true then the tire should accelerate by itself.

What do you mean by applying this case to every case ??

The frictional force here is opposing the tendency of the tire to slide back ward when it is moving forward not the translation motion of the tire itself ..,,

 

[oreo]

What do you mean by applying this case to every case ??

The frictional force here is not opposing the tendency of the tire to slide back ward when it is moving forward not the translation motion of the tire itself ..,,

It would oppose if the tire is stationary but it is in motion. If it is in direction of motion like you are saying then the tire should accelerate. Isn't it

 

[Maged Saeed]

Actually we say that the tire is touching the ground with one point , and ,this point is not moving during the contact time and we say that the work done by the frictional force is ZERO since it is not making any sliding to the tire , and that is IF the tire is not sliding .