Question

a body is moving along a circular path of radius R .what will be the distance travelled and displacement the body when it completes half revolution

Answer 1

$displacement \: = diameter \\ nd \: distance \: = \pi \: r$

Answer 2

perimeter of the circle = 2πR
when it completed half revelation then
it distance will be 2πR/2 = πR

displacement means the shortest path traveled by object
when it completed half revelation then displacement will be
= 2R or diameter of the circle