Question

A boy completes one round of circle if radius R in 20sec.the displacement to distance after 10sec

Answer 1

the boy completes one round in 20 sec

no of rounds covered in 10 sec=10/20=1/2 round

the distance covered is equal to the actual path covered by the object

$distance = 2\pi \: r$

displacement is the shortest distance covered by the object between it's initial and final position

$displacement = r + r = 2r$

$\frac{displacment}{distance} = \frac{2r}{2\pi \: r} = \frac{1}{\pi}$

I hope this helps ( ╹▽╹ )