Why does the frictional force in case of circular motion point towards the center even though the motion is tangential to the radius?
[Physics] The direction of frictional force in circular turning
frictionrotational-dynamicsrotational-kinematics
Related Solutions
Frictional force opposes sliding motion, basically. Car tires produce centripetal force by changing their angle relative to the rest of the car's orientation. The tires do not slide in the direction of the tires' orientation: they roll. Friction in this direction rotates the tires, or if the engine is applying force to the wheels during the turn, friction prevents the tires from "burning rubber", and pushes the car in this direction.
Meanwhile, motion in the direction of the rest of the car's orientation is opposed by friction only to the extent that it is not motion in the direction of the tires' orientation. The velocity vector corresponding to the rest of the car's orientation can be understood in terms of these two orthogonal components. The component corresponding to the tires' orientation is basically not subject to friction for our purposes (ignoring whether one's foot is on the gas pedal). The component that does not correspond to that other component is orthogonal and opposed by centripetal friction.
Based on GIF by Droidmakr.
If tires' orientation $=$ rest of the car's orientation, basically no centripetal friction results.
Friction forces act as a response, and opposite, to velocity, not force (that would be normal forces).
The car has a liner velocity in the forward direction, and it keeps moving indefinitely, ignoring any residual friction. Then, if the steering wheel is turned left, the front tires are rotated to the left, thus there appears a frictional force perpendicular to those tires. This force is caused by the tires resisting the movement, just as any other friction. The interesting thing is that tires can rotate freely only in one direction, but not in the perpendicular. Thus the friction appears only in that non-rotating direction.
This force will point not perpendicular to the car, but perpendicular to the tires. The difference is small, since the actual angle that the tires are rotated is quite small, particularly at high speeds. Also, once the car is rotated from the straight line, a small lateral friction will appear also in the back tires, because the velocity will no longer be aligned with the axis of the tires.
Best Answer
The force of friction acts both towards the centre of the circle and opposite the velocity vector of the car. Strictly speaking, the diagram you have does not show all forces acting on the car but it is enough for purposes of explaining the circular motion.
As the text also explains, circular motion always requires a force pointed radially inwards because the object is changing its velocity. Newton's first law of motion tells us that a change in motion requires a force to act on the object.
A car driving through a curve "wants" to go in a straight path because of its inertia but it actually takes a turn. Because the force that provides the centripetal acceleration opposes the natural tendency of the car to move outwards, it is feasible for this force to be frictional in nature.