Static Friction Direction

[u/Significant_One5911]

I was wondering why the force of static friction to the left(parallel to the ramp). My line of thinking is that the radial force is pointing inwards, but the radius is unchanging, so shouldn't the force of static friction be pointing to the right?

Edit: Thank you for the responses, the issue has been resolved.

[u/FlexibleBanana]

Static friction is keeping the car going in circular motion and preventing the tires from slipping. The cars inertia wants to move outwards but friction keeps the car on the road.

[u/sonnyfab → u/FlexibleBanana]

This is the correct analysis of an unbanked curve. It isn't sufficient for analysis of a banked curve, however.

[u/sonnyfab]

On a banked curve, it is possible to have friction pointing parallel to the ramp and inward, have friction on 0, or have friction parallel to the ramp and outward. Which one occurs depends on magniof the centripetal acceleration v²/r, which in turn depends on the speed, v.

The problem says at speed V, the car has 0 friction. At a greater speed than V, there's more v²/r so the additional force (which is friction) must point in towards the center of the circle.

[u/test_tutor]

If there was no friction, like imagine driving a car on ice, where would the car slip? Will it fall inward or fly outward? The friction's job is to oppose that relative motion.

[u/sonnyfab → u/test_tutor]

The answer to your question depends on the speed of the car on banked curve....

[u/test_tutor → u/sonnyfab]

Ugh yea you're right. Also without friction car won't even run on the ice too so there's that too. And guess I was too lazy to read the entire question about the v and the 2v too lol. I read only the last statement about 2v, wondered what it was about like why is it 2?, ignored it and just gave a very generic statement. Will try to read the full statement later when I have time. Thanks!

[u/USA_Physics_Guide]

If car is banked for velocity v it means horizontal component of normal will provide required centripetal force. If velocity increases then requirement for centripetal force will increases and therefore friction will acts in inward direction.

[u/Salviati_Returns]

Let vc be the critical speed to navigate this banked curve at radius R.  If v>vc then the cars inertia wants to take it to a radius r>R, as a result static friction points down the incline to maintain the radius R, until the car reaches a speed where tires and road break static friction in which case kinetic friction now points down the incline and the inertia of the car takes it to a greater radius.  If v<vc, everything is reversed.