TransWikia.com

Deciding if static or kinetic friction is acting on a system

Physics Asked on April 30, 2021

In this recent question which discusses about why it is static friction which acts on a moving car. User Neelim answered this question with an explanation based on the condition of non accelerated rotating and hence there is no actual relative motion between road and the car wheels here

This leads me to my variant of the question: Suppose instead of a car, we had a box set to move in the circular path by action of some forces. Would static friction act still in the centripetal direction?

In other words, does the presence of motion in a tangential direction have any control over the friction which acts in the centripetal direction?

Note:

The reason I told box is to have a flat surface w/o rolling.

2 Answers

The static friction in the centripetal direction is because of skidding.

You might have seen the skid marks on the turns. This skidding motion is away from the centre of the track and hence this skidding relative motion leads to the centripetal static friction force.

Indirectly we can say that the static friction force was due to the tangential velocity since this tangential motion caused skidding.

Hope it helps ?.

Correct answer by Ankit on April 30, 2021

Your question is a bit to broad, so I will try to break it down into simpler to analyze chunks.

In a moving car the only force doing work is friction (both while accelerating and curving). You "push" the floor, and it pushes you back in the direction you want to go (imagine walking on a piece of ice, in this case locomotion is difficult because there is little friction). So, it is always friction that makes a car move.

In the case of the box, it depends on the source of locomotion. If the box is propelling itself with wheels, it is a car. If it uses a fan, or someone is pushing it around, then these would be the sources of the force that makes it go around the curve.

In the case of a car, the reason why static friction is the responsible force is because the patch of the wheel in contact with the floor has zero velocity (relative to the floor). In the case of a box, this would be impossible (unless it has wheels and is a car).

Answered by JGBM on April 30, 2021

Add your own answers!

Ask a Question

Get help from others!

© 2024 TransWikia.com. All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP