A 5000 kg rocket is set of vertical firing. The exhaust speed is `800" "ms^(-1)`. To give an initial upward acceleration of `20ms^(-2)`, the amount of gas ejected per second to supply the needed thrust will be (take, `g=10ms^(-2)`)

Options

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

Answer

B

Explanation

`F = v ((dm)/(dt)) = m(g+a)`
`rArr (dm)/(dt) = (5000 xx (10 + 20))/(800) `
` = (1500)/(8) = 187.5 kg //sec`