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Distance and Displacement | How are they different?

Distance and displacement are two quantities, one is scalar(distance), and one is vector(displacement) but they still seem to mean the same thing. 

Let us understand what these concepts mean, and how they are different.


What is Distance?
Distance is a scalar quantity that refers to the length of the path which an object has covered during its motion.

A__________B________C

Let A, B, and C be three points which form a straight line. An object starts at point A and travels through B and reaches C, and then it moves back along the same path to get back to A through B.

In this case the distance travelled by the object is twice the length from A to C.

In order to describe distance, we only need to specify the numerical value and not the direction of motion. This numerical value is called as the magnitude. This is the reason why distance is a scalar quantity.


What is Displacement?
Displacement is a vector quantity that refers to the shortest distance measured from the initial to the final position of an object.

A__________B________C

Let's take the exact same scenario where  A, B, and C are three points which form a straight line. An object starts at point A and travels through B and reaches C, and then it moves back along the same path to get back to A through B.

There will actually be no displacement here. This is because the object has come back to where it originally started. The initial and final positions are the same.

To describe displacement, we need to consider the magnitude as well as the direction of Motion. This is why displacement is a vector quantity.

When you travel on road, for example, you make a lot of turns and your direction of motion keeps changing. 

When you reach your final position, even though you may feel like you have travelled for a long time(and you have travelled a large distance), the shortest distance in a straight line from your initial position to your final position, that is the displacement, can actually be much shorter than the actual distance, that is the length of the path you have covered.


Can the distance be equal to the displacement?
Yes, of course the distance and displacement can be equal.

If an object travels in a straight line without changing its direction, then it will already be travelling the shortest distance to reach from the initial position to the final position. This means that the distance and displacement will be the same.



In physics, distance and displacement are used to describe the overall motion of an object and to determine its final position with respect to it's initial position at a given time.


There are devices which measure the distance travelled. Such a device is called as an odometer. You can find such devices in automobiles.

I think you should be able to understand the concepts of distance and displacement well now. I hope you learned something new today by reading this blog post.

Thank you for reading!

- Arya Bharaty




 
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