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# A 600 kg rocket is set for a vertical firing. If the exhaust speed is 1000 m/s. The mass of gas ejected per second to supply the thrust needed to overcome the weight of the rocket is

$(a)\;5.88 \;kg/s \quad (b)\;4.88\; kg/s \quad (c)\;2.88\; kg/s \quad (d)\;3.88\; kg/s$

Force required to overcome the weight
$F=mg=v\large\frac{dm}{dt}$
$\large\frac{dm}{dt}=\frac{mg}{v}$
$\qquad=\large\frac{600 \times 9.8}{1000}$
$\qquad=5.88 \;kg/s$
Hence a is the correct answer.
edited May 27, 2014