A 5000 kg rocket is set for verticle firing. The relative speed of burnt gas is `800ms^(-1)`. To give an initial upwards acceleration of `20 ms^(-2)`, the amount of gas ejected per second to supply the needed thrust will be

Options

A. `127.5 kg s^(-1)`
B. `137.5 kg s^(-1)`
C. `187.5 kg s^(-1)`
D. `185.5 kg s^(-1)`

Answer

C

Explanation

`F=(dp)/(dt), m(g +a) = (dm)/(dt) vrArr(dm)/(dt)=(m(g+a))/(v)` .