# If I'm driving a car and I make a turn to the right, what will happen to a bag of items that is...

## Question:

If I'm driving a car and I make a turn to the right, what will happen to a bag of items that is sitting next to me in the car in terms of inertia, friction and centripetal force?

They will fall the opposite direction.

Why?

## Rotating Frame Of Reference

When motion is analyzed in an accelerated frame of reference or a non-inertial frame, it is not possible to directly apply Newton's laws if we consider only the contact forces and the long-range forces. An object of mass M will experience a fictitious or pseudo force {eq}\displaystyle {- Ma} {/eq} if the acceleration of the frame is {eq}\displaystyle {a} {/eq}. This is what happens when you are inside a vehicle which suddenly accelerates forward. You are thrown backward even though there is no visible agency pushing you backward. If the fictitious forces are taken into consideration over and above the contact and long-range forces then Newton's laws will work fine. Acceleration can arise either by the change in the magnitude of the velocity or by the change in direction. In a uniformly rotating frame of reference, acceleration arises on account of the change in direction. Now two fictitious forces called the centrifugal force and the Coriolis force arise.

When a car takes a curve it follows the arc of a circle. Now the acceleration of the car is directed towards the center of the circle. Normally the friction due to the road provides the centripetal force responsible for this. The car defines a rotating frame since the direction of its velocity is changing. Thus all objects inside the car will experience a fictitious force away from the center of the circle. This will drive them outwards. The fictitious force is called the centrifugal force.

When the car takes a right turn as given in the problem, the centrifugal force is directed to the left. Hence the objects inside the car will fall towards the left. This may be visualized as follows. Initially, the car and all the objects in it are traveling at the same speed. But now the car suddenly swerves to the right. This is done with the help of the friction provided by the road. But the objects inside the car tend to maintain their initial velocity on account of the inertia or the mass they possess. Thus in the car frame which is turning right, they 'appear' to be moving to the left. Since there are no preferred frames of reference in physics what we observe is just about as real as it gets.