Question

A particle is moving along a circular track of diameter 10 . what is its distance and displacement after 2 and half revolutions?

Answer 1

now let us say that the particle starts from point A anywhere on the circular track.....   after 2 and a 1/2 revolutions it will reach to a point (say) B which will be diametrically opposite to A .........

since , displacement is the shortest distance covered by a body

therefore displacement would be the diameter of the track

                  displacement = 10 m

now talking of distance .........

the body covered 2 rounds of circle  i:e  2(2\pi[/r])

and a half round i:e \pi r

therefore total distance = 4 pie r + pie r

                                           4 *3.14*5 + 3.14* 5

                                           = 78.5 m