What is the Direction of Frictional Force in Pure Rolling?

In summary, a wheel of radius 20cm is pushed on a rough horizontal surface and moves through a distance of 60cm in one revolution. The frictional force acting on the wheel is in the direction opposite to the velocity of the wheel. However, if the wheel is slipping, the friction will act in the forward direction.
  • #1
utkarshakash
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Homework Statement


A wheel of radius 20cm is pushed to move it on a rough horizontal surface. It is found to move through a distance of 60cm on the road during the time it completes one revolution about the centre. Assume that the linear and the angular accelerations are uniform. The frictional force acting on the wheel by the surface is
a)along the velocity of the wheel
b)opposite to the velocity of the wheel
c)perpendicular to the velocity of the wheel
d)zero

Homework Equations



The Attempt at a Solution


Let us suppose that the friction is static and thus pure rolling occurs. The friction will act in the forward direction ie along the direction of velocity.
Since pure rolling occurs
[itex]v=\omega r[/itex]
The angular displacement is 2∏ rad
The perimeter of the wheel is 2∏*0.2 metres
Since pure rolling occurs the linear distance covered should be equal to (2∏*0.2)metres as only one revolution occurs. But the actual linear distance covered is 0.6 m. This means that our assumption is incorrect and thus kinetic friction acts in the backward direction. So answer should be (b) but it is (a). Where is the fault?
 
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  • #2
The wheel is being driven (presumably by an axle) but it is 'slipping'. Think about the point where the wheel is in contact with the ground.
Which way is it sliding?
 
  • #3
AJ Bentley said:
The wheel is being driven (presumably by an axle) but it is 'slipping'. Think about the point where the wheel is in contact with the ground.
Which way is it sliding?

It must be sliding backwards.
 
  • #4
If it's sliding backwards, which way is the friction?
 
  • #5
AJ Bentley said:
If it's sliding backwards, which way is the friction?

It must be forward which is the correct answer. Thanks!
 

FAQ: What is the Direction of Frictional Force in Pure Rolling?

1. What is the direction of frictional force?

The direction of frictional force is always opposite to the direction of motion or attempted motion between two surfaces in contact. This means that if an object is moving to the right, the frictional force will be directed to the left, and vice versa.

2. Does the direction of frictional force always oppose motion?

Yes, the direction of frictional force always opposes motion between two surfaces in contact. This is because friction is a resistive force that acts to prevent or slow down the movement of objects.

3. Can the direction of frictional force change?

Yes, the direction of frictional force can change based on the direction of motion or attempted motion between two surfaces. For example, if the object is sliding to the left, the frictional force will be directed to the right. If the object changes its direction and starts moving to the right, the direction of frictional force will also change to the left.

4. Is the direction of frictional force the same for all types of surfaces?

No, the direction of frictional force can vary depending on the type of surfaces in contact. For example, the direction of frictional force between two rough surfaces may be different from the direction between two smooth surfaces. The type of surface and the amount of force applied can affect the direction of frictional force.

5. How does the direction of frictional force affect the motion of objects?

The direction of frictional force can either increase or decrease the motion of objects, depending on the direction of motion. If the object is already in motion, the frictional force will act to slow it down. However, if the object is at rest, the direction of frictional force can help to initiate motion by providing the necessary force to overcome static friction.

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