# Doubt from friction

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1. Dec 14, 2015

### ajaysabarish

• Member warned about proper use of the template and showing an attempt at solution.
please explain the phenomenon of friction acting on a car moving in a circular track.also explain how is this friction static and how is this friction different from the friction acting on a car moving on a straight road.

2. Dec 14, 2015

### haruspex

As per forum rules, you must show some attempt at a solution. List any standard equations or principles you believe may be relevant.

3. Dec 15, 2015

### ajaysabarish

thank you very much for replying,sir.this isn't any homework question but a doubt, i got while solving problems.when i was trying to attempt problems involving friction in a circular track,i found it very much different from friction in a straight track.for example the direction of friction was no more opposite to direction of relative motion,and the friction is considered to be static while the car is moving.so please explain the entire phenomenon of friction acting on a circular track for car,particle,etc.

4. Dec 15, 2015

### CWatters

The car isn't skidding so the tyres aren't sliding over the surface.

5. Dec 15, 2015

### haruspex

Friction opposes relative motion of the surfaces in contact. That means it acts not only against any actual motion but also against any tendency to motion.
For a rolling wheel at constant speed in a straight line on a level, stationary surface, there is no tendency to relative motion. The part of the tyre in contact with the ground would be stationary relative the ground even without friction (so there isn't any). Only when the wheel speeds up or slows down, or changes direction, or starts to go up or down a slope, will there be any risk of sliding.
It's not to with whether the car is moving. What matters is whether the tyres are in rolling contact.