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=10ms^(-2)`)

Options

A. `sqrt(2) s`
B. `2 pi sqrt(2) s`
C. `2 s`
D. `2 sqrt(2) s`

Answer

D

Explanation

Velocity at point `p=sqrt(((m)/(L)gx)/(m//L))`
`v = sqrt(gx)`
`(dx)/(dt)= sqrt(gx)`
`underset(0)overset(20)(int)(dx)/(sqrt(x))=underset(0)overset(t)(int)sqrt(g)dt`
`t = 2 sqrt(2)sec`