Question

An object goes from point X to Y and then comes back from Y to X. What is the displacement and average velocity?

Answer 1

Use concept of displacement and average velocity. Shortest distance travelled is nothing but displacement while ratio of displacement and time is known as average velocity. Average velocity depends on displacement and time. Distance is the total path covered.

Complete step-by-step answer:
First let’s understand what displacement and average velocity is?
Distance and displacement are two terms which are used while introducing length. Distance is the total path covered by the body while displacement is the shortest distance covered by the body between two points.
Similarly there are two types of velocity: average and instantaneous velocity. The displacement of the particle in a time interval is equal to the distance travelled in that interval. So the magnitude of the velocity will be the instantaneous speed at time. Instantaneous velocity is also called the "velocity". While average velocity is the difference between distances of two points per time.
That is we can say that velocity is a ratio of displacement and time.
In this question. Body travels from starting position X up to ending position Y and then it again comes back from ending position to starting position. Since displacement is the shortest distance between starting and ending point therefore displacement of the body goes from point X and Y and again comes back from Y to X is zero.
If you will put this value of displacement in average velocity then the value of average velocity will be zero.
Therefore, both displacement and average velocity will be zero.

Note: Displacement is the vector quantity while distance is the scalar quantity. Note that no matter along which path the body has travelled, if it comes to its original position then its displacement is zero. Also note that the instantaneous velocity and average velocity are two different things. The average velocity is the velocity of the body over a given interval of time whereas the instantaneous velocity is the velocity of the body at a particular instant of time.
If the instantaneous velocity is zero then the body is in the state of rest.