A man generates a symmetrical pulse in a string by moving his hand up and down. At t = 0, the point in his hand moves downwards from mean position. The pulse travels with speed `3m//s` on the string and his hand passes 6 times in each second from the mean position. Then, the point on the string at a distance 3 m will reach its upper extreme first time at t =

Options

A. 1.25 sec
B. 1 sec
C. `13/12` sec
D. none

Answer

A or C or D

Explanation

`f=3 Hz " " rArr T=1/3 sec`
`lambda=1m`
His hand at upper extreme at `(3T)/4=1/4` sec
This message reaches x=3 at t=1 sec. later.
`rArr 1.25 sec`