You're sitting in the passenger seat of a racing car that is moving rapidly along a level track. The track takes a sharp turn to the left, and you find yourself thrown against the door to your right. What horizontal forces are acting on you, and what feelings of acceleration do you experience?

When you're in a racing car making a sharp turn, you might feel like you're being pushed to the side. This feeling is due to centripetal force. Centripetal force is the force that keeps an object moving in a circular path. It always points towards the center of the circle.

In our case, as the car takes a left turn, the centripetal force is directed towards the left. The door of the car provides this force by pressing against you. Without this force, you would continue moving in a straight line due to inertia. This is why it feels like you're being thrown to the right. But in reality, it's the car and door providing the necessary centripetal force to keep you moving in a circular path.

Inertia is a fundamental concept in Newtonian physics. It refers to the property of an object to resist changes in its state of motion. In simple terms, an object at rest stays at rest, and an object in motion stays in motion with the same speed and direction unless acted upon by a force.

When the car makes a sharp turn, your body wants to continue moving forward in a straight line (thanks to inertia). However, the car is turning left. This discrepancy between your body's inertia and the car's movement causes the sensation of being pushed to the right. But, it's just your body's resistance to change in direction.

A non-inertial reference frame is a frame of reference that is accelerating. When you're inside the racing car turning left, you're in a non-inertial reference frame because the car is accelerating. In this frame, it feels like there's a force pushing you to the right.

This 'force' is known as a fictitious or pseudo-force because it arises due to the acceleration of the reference frame itself. In reality, there's no physical force pushing you rightwards. It's just the effect of being in an accelerating (non-inertial) frame. Understanding this helps us comprehend why we feel pushed against the door during the turn.

Circular motion involves any motion in a circular path. Key to this motion is the continuous change in direction, which means there is always acceleration even if the speed is constant. This acceleration is called centripetal acceleration and it points towards the center of the circle.

In our scenario, as the car makes the left turn, you are experiencing circular motion. The car door provides the centripetal force needed to keep you moving in that circular path. Without this force, your inertia would cause you to move straight off the circular path. Hence, despite feeling like being pushed outwards, you're actually being accelerated inwards towards the center of the circular path formed by the turning car.