Distance vs displacement


Show/Hide Sub-topics (Speed, Velocity and Acceleration | O Level)

Distance travelled by an object is the length of path taken.

Displacement is the shortest distance from the initial to the final position of an object.


Distinguishing Between Distance and Displacement

If you have problems grasping the difference in concept of displacement and distance travelled, please study the example below.

Displacement vs distance

Consider the diagram above:

Difference between distance and displacement: If an object started travelling from B to C and ends at D, distance travelled is BC + CD. Displacement is BD.

Displacement can be ZERO: If the object started travelling from B to C to D and ends at B, distance travelled is BC + CD + DB. Displacement is ZERO. (The object ends at the same place it started)

Displacement can be NEGATIVE: If the object travels from B to A, the displacement is negative. By CONVENTION, the direction towards the right and top are positive. A way to remember: Go right = positive, go left = negative.


Examples

Ali walked 1 km to the North, then 1 km to the East and followed by 1 km to the South. What is the distance covered by Ali? What is his final displacement?

Show/Hide Answer

Distance: $1 + 1 + 1 = 3 \, \text{km}$

Displacement: 1 km east of starting point.


A car travelled from point O to D along the curved path OABCD. What is (a) the distance travelled by the car, and (b) the displacement of the car?

Show/Hide Answer

The distance travelled by the car is OABCD.

The displacement of the car from point O is OD (to the right of O).


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4 thoughts on “Distance vs displacement”

  1. I don’t get how displacement can be negative…Can u please explain soon?
    Otherwise i think it’s the best website,,, Thumbs up!!!

    Reply

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