How does a car changing direction work? [duplicate]

Question

If a car is attempting to accelerate forward, it begin by spinning its wheels. At first the car won't be moving, so if the wheels were to begin spinning without the car moving, there would be a relative motion between the wheels and the road. In essence, because of an instantaneous relative acceleration between the wheels and the road, there would be a static friction opposing that relative acceleration, propelling the car forward.

I'm confused as to how this logic applies when driving a car. How does the act of turning the direction the front wheels point cause the corresponding static friction to act as a centripetal force? In particular, wouldn't the relative motion cause the static friction to act parallel to the direction of the wheels (like in the linear acceleration case), rather than perpendicularly?

Answer 1

it begin by spinning its wheels. At first the car won't be moving, so if the wheels were to begin spinning without the car moving, there would be a relative motion between the wheels and the road.

That describes a skid. It would work but be inefficient. Instead for most cars and drivers, the engine applies a torque to the wheel. The ground applies a counter-torque that is less. The wheel starts spinning and moving forward at the same time.

How does the act of turning the direction the front wheels point cause the corresponding static friction to act as a centripetal force?

If we stop the engine torque and don't apply the brakes (the car is coasting), then the wheels are very easy to spin. This means that any attempted movement perpendicular to the axis is nearly unopposed. When coasting, no significant forces arise perpendicular to the axis.

But the same is not true for movement parallel to the axis. Any attempt in that direction can't be accommodated by the wheel turning, so high frictional forces arise.

With the car moving forward, when the steering wheel is turned the motion of the car forward can be split into a component perpendicular and parallel to the wheels axis. Forces arise to oppose the parallel motion. This force on the front of the vehicle causes the car to rotate.