Why Does Friction Act in the Same Direction as the Force on a Rotating Disc?

[sArGe99]

Homework Statement

"Friction hinders translation but aids rotation"
If a uniform disc is placed on a surface and a force is applied tangential to it, why is the direction of friction same as that of the force. This would surely hinder rotation and aid translation, right?

Homework Equations

This is not a problem.

The Attempt at a Solution

Out of ideas. Thought a lot about it.

 

[fanman791]

I believe what they are trying to say is when the disk spins, it is pushing the surface in the opposite direction of which it is moving. Think about it: when you push against the ground, you move in the opposite direction of your push. Therefore, the friction is in the opposite direction of which it is spinning.

 

[nlightner]

I can provide some insight into the direction of frictional force in this scenario. First, it is important to understand that friction is a force that opposes motion between two surfaces in contact. In the case of a disc on a surface, the frictional force acts in the opposite direction of the applied force, which is tangential to the disc. This is because the disc is trying to rotate in the direction of the applied force, and the frictional force acts to prevent this rotation.

However, it is also important to consider the relative magnitude of the forces involved. In this scenario, the applied force is likely much larger than the frictional force, so the disc will still experience a net force in the direction of the applied force. This means that the disc will still experience some translation, but the frictional force will act to slow down the rotation of the disc.

In summary, the direction of the frictional force is opposite to the applied force because it is trying to prevent rotation, but the magnitude of the applied force may still result in some translation. This is why friction is often described as hindering translation but aiding rotation.