Question

an athlete completes one round of circular track of radius R in 40 second what will be his displacement at end of 2minutes 20 second

Answer 1

2minutes 20 secinds=3.5 rounds
circumfrence=2pieR
displacement=7x22/7xr
=22r

So the displacement will be 22r

Answer 2

Nope, displscement is a vector.

displacement= ending position-starting position.

As I calculate, he is opposite his starting position, or 2R, in the direction opposite the starting point. In polar coordinates, the displacement is
2R@180