A uniform string of length 20 m is suspended from a rigid support. A short wave pulse is introduced at its lowest end. It starts moving up the string. The time taken to reach the support is : (take $g = 10\; ms^{−2}$ )

Question

( A ) $2 \; s$
( B ) $2 \pi \sqrt{2} \; s$
( C ) $ \sqrt{2} \; s$
( D ) $2 \sqrt{2} \; s$