# Frame of Reference – an Intuitive Explanation

While I was explaining about force, I mentioned about the frame of reference. This part confused me a lot in my physics class, but soon with some reading, I was able to understand it completely now. Here is an intuitive way to understand the concept of this.

## Frame of reference

A frame of reference is nothing more than a Cartesian coordinate system fixed to something. This ‘something’ could be either a stationary ground or a moving car. Consider the frame of reference as an imaginary tool to measure the position, speed and direction of a moving car relative to a yellow wall on the side of the road. As the wall is fixed to the ground and so do you, you and the wall are in the same frame of reference. Now you could easily measure the position and velocity of the car by drawing an x-axis on the yellow wall in the direction of the moving car.

A frame of reference can be anywhere. It can be moving too. Place the same point inside a moving car and form a Cartesian coordinate system inside it. You can call that as a frame of reference too. There are two frames of reference.

## Inertial frame of reference

An inertial frame of reference is observed when the car’s velocity doesn’t change when we observe it from a stationary frame of reference or from the car’s frame of reference. While there are forces from friction and earth’s rotation that could change this constant velocity, we neglect these negligible effects and consider it as an inertial frame of reference.

## Non-inertial frame of reference

A non-inertial frame of reference is a little tricky to explain. Considering only the Newtonian physics, it can be explained as a frame in which the object accelerates or change its state of motion. During this, the object is said to have pseudo forces like the force that pushes you back on the seats when the bus starts to move.

I believe this helped you to understand what an inertial frame of reference and a non-inertial frame of reference is. If you have any further questions, send me an email to my yahoo ID.

This post was first published on May 13, 2005.