Note:- This is not the first time this question has been asked (far too many to link), but everytime it was asked as "why does friction cause a car to turn?" where rolling and rotation of the wheels got involved and made everything complicated. None of them seem to answer the more basic question that I have in mind.
I have been taught in physics class that static friction acts opposite to the direction of impending relative motion while kinetic friction acts opposite to actual relative motion, which seems to be the most general statement regarding friction direction. However lets consider a block (pt. mass) kept on a rough disk. The disk is spinning at a uniform constant angular velocity $\omega$ and the block is dropped onto the disk, initially at rest (the block not the disk). By even common sense we can see that the block will speed up until it has the velocity $\omega r$ where r is the distance of the block from the centre of the disk. In the steady state, the block spins along with the disk.
Q: Initially, why does the friction cause the block to go in a circle around the centre? (I think I understand what happens in steady state: the direction of impending motion is radially outward in the disk frame so friction acts radially inward.)
Qa): Is the statement "static friction acts opposite to the direction of impending relative motion" always correct?
Qb): What is happening in the case of a car turning on an unbanked road? Here the direction of ACTUAL relative motion is tangential and in the direction of car velocity, why should friction act radially instead of tangentially? Also is that force rolling friction?
PS: I am sorry for the word salad, will break into smaller qs if community says so.