Question

Define inertial and non-inertial frame of reference. Give examples.

Answer 1

Hint: Study about the frame of reference. Try to differentiate between inertia and non-inertial reference frames. Try to understand Newton's laws of motion and in which situation we can apply them.

Complete step-by-step answer:
Frame of reference can be defined as an abstract co-ordinate system of the body. A frame can be at rest or moving depending on the body we see. If the body is moving then also, we can define an abstract co-ordinate system for the body with reference to some physical point at which the body is at rest. Depending on this frame of reference we can formulate the physical laws on that system.

We have two kinds of frame of reference.
1. Inertial frame of reference
2. Non-inertial frame of reference

Inertial reference frames can be defined as the reference frame at which we can apply Newton's laws of motion. If no external force is applied a body at rest will remain at rest and a body in constant motion will remain in constant motion. The concept of inertial reference frame is relative. First, we consider the reference frame to be inertial. Then we can define another frame which is at rest or at constant velocity with respect to the reference frame. Consider you are observing a moving at constant velocity with respect to you. Then you can apply the same Newton’s laws of motion on any object inside the car. If we consider a coordinate system for the moving car at constant velocity then the frame will be an inertial frame.

Non-inertial reference frame can be defined as a frame where an external force is applied or the frame is accelerating with respect to the reference frame. In this reference frame Newton's laws of motion do not hold true. Consider the same car as the above. Now, if you observe the car as the driver pulls the brake the car will decelerate. But the object inside the car will move towards the front. There is no force acting on the object. It will move just because the car is decelerating. This is an example of a non-inertial frame of reference.

Note: The concept of inertial reference frame is relative. If two objects are accelerating opposite to each other we cannot define an inertial frame because there is no reference. We can define one of them as inertial and the other as non-inertial but we cannot choose which one to be inertial