A uniform string of length `20m` 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. 2s
B. `2 sqrt(2) s`
C. `sqrt(2) s`
D. `2 pi sqrt(2) s`

Answer

B

Explanation

Velocity at point `P = sqrt((T)/(mu)) = sqrt(((m)/(L) gx)/(m//L))`
`upsilon = sqrt(gx)`
`(dx)/(dt) = sqrt(gx)`
`underset(0)overset(20)int (dx)/(sqrt(x)) = underset(0)overset(t)int sqrt(g) dt`
`|2 sqrt(x)|_(0)^(20) = |sqrt("gt")|_(0)^(t)`
`t = 2 sqrt((20)/(10)) = 2 sqrt(2)` sec
`t = 2 sqrt(2)` sec