A boat B is moving in upstream with velocity `3 m//s` with respect to ground. An observer standing on boat obsserves that a swimmer S is crossing the river perpendicular to the direction of motion of boat. If river flow velocity is `4 m//s` and swinner crosses the river of width `100m` in 50 sec, then

Options

A. Velocity of swinner w.r.t. ground is `sqrt(13m^(2)//s^(2))`
B. Drift of swimmer along river will be zero
C. Drift of swimmer along river will be `150 m`
D. Velocity of swimmer .w.r.t ground is `2 m//s`

Answer

A, C

Explanation

`vec(v)_(SB) = v hat(j) = vec(v)_(s) - 3 hat(i)`
`rArr vec(v)_(S) v hat(j) + 3 hat(i)` and `v = (100)/(50) = 2 m//s`
`|vec(v)_(s)| = sqrt(v^(2) + 3^(2)) = sqrt(13m^(2) //s^(2))`
Drift `= 50 xx 3 = 150m`