Why static friction not kinetic in this problem?

[Tahmeed]

Homework Statement

The sports car ) is rounding a flat, unbanked curve with radius R . If the coefficient of static friction between tires and road is Us, what is the maximum speedat which the driver can take the curve without sliding?

why in this problem i am given Static fiction coefficient instead of kinetic?

 

[ehild]

Homework Statement

The sports car ) is rounding a flat, unbanked curve with radius R . If the coefficient of static friction between tires and road is Us, what is the maximum speedat which the driver can take the curve without sliding?

why in this problem i am given Static fiction coefficient instead of kinetic?

Because we do not want the car sliding out of the curved track. The piece of tyres in contact with the asphalt should not move relative to it.

 

[Tahmeed]

can you clear?? i didn't get it.

 

[CWatters]

Ask yourself...

Which direction is the friction acting?
Is the car moving in that direction?

 

[haruspex]

why in this problem i am given Static fiction coefficient instead of kinetic?

Friction relates to surfaces in contact. The choice of static or kinetic friction is determined by whether there is relative motion between the two surfaces. The motion of the car is not important; what matters is whether the part of the tyre in contact with the road is moving relative to the road - i.e. skidding.
See section 3.2 of https://www.physicsforums.com/insights/frequently-made-errors-mechanics-friction/

Which direction is the friction acting?
Is the car moving in that direction?

That's not really the key. An accelerating car on the flat can experience static friction in the direction of motion without skidding.

 

[CWatters]

That's not really the key. An accelerating car on the flat can experience static friction in the direction of motion without skidding.

Insert embarrassed face here :-)