An indian submarine is moving in the Arabian sea with constant velocity. To detect enemy it sends out sonar waves which travel with velocity `1050(m)/(s)` in water. Initially the waves are getting reflected from a fixed island and the reflected waves are coming back to submarine. The frequency of reflected waves are detected by the submarine and found to be `10%` greater than the sent waves.
Now an enemy ship comes in front, due to which the frequency of reflected waves detected by submarine becomes `21%` greater than the sent waves.
Q. The speed of indian submarine is

Options

A. `10(m)/(s)`
B. `50(m)/(s)`
C. `100(m)/(s)`
D. `20(m)/(s)`

Answer

B

Explanation

`f'=f_0((v+v_1)/(v-v_1))`,`v=1050`
`f'=(110f_0)/(100)`
Solve to get `v_1=50(m)/(s)`