Chapter 10, Problem 43A

When you are in the front passenger seat of a car turning left, you may find that you feel pressed against the right door. Why do you press against the door? Does the door press on you? Does your explanation involve a centrifugal force or Newton’s laws?

To determine

To Explain:Passenger presses against door as well as door presses on passenger when car turns.

Explanation of Solution

Introduction:

When car moved along the straight path with uniform velocity, forces acting on the car are:

1. Weight of the car
2. Normal reaction force.

Normal reaction force balances the weight of the car. So net unbalanced force acting on the car is zero and body continues in motion.

When car move along curved path, the forces acting on the car are:

1. Weight of the car
2. Normal reaction force.
3. Centripetal force towards the center of the curvature
4. Frictional force between the tires of the car and road.

When car moves along the straight path, weight of the car is balanced by the normal reaction force. The car moves along the curved path because of centripetal force acting on it along the center of the curvature. This centripetal force is balanced by the frictional force between tires of the car and road. Direction of frictional force is away from the center of the curvature.

Velocity is acquired by the passengers when car moves uniformly in straight line. When car is turned left around a curved path, due to centripetal force, the car moves towards the center. This centripetal force is balanced by the frictional force of the tires of the car. Due to the change in the direction of the car, velocity of the car changes which results into the net force experienced by the passengers inside the car. Due to inertia, there is no balanced force experienced by passengers inside the car.Hencepassengers move right side in the car. So, according to the Newton’s first law of motion, change in inertia of passengers, moved them to right side in the car. Due to inertia, passengers push against the door with force. According to Newton’s third law of motion, the door exert equal amount of force on the passengers. Due to that force passengers experience the push from the door.

Conclusion:

Passengers moved to the right when car turned to the left because of the Newton’s law of inertia. Similarly, when passengers move to the right door, they experience the net push from the door side. This push is due to the Newton’s third law of motion.