A 4000 kg rocket is fired. If the exhaust speed is 500 ms–1 , how much gas must be ejected per second to supply the thrust needed, (a) to overcome the weight of the rocket, (b) to give the rocket an initial acceleration of 9.8 ms–2 ?

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An Intiative by Sri Chaitanya

58.8 Kg/s ; 176.4 Kg/s

132.8 Kg/s ; 82.5 Kg/s

78.4 Kgs–1 ; 156.8 Kgs–1

93.2 Kg/s ; 185.6 Kg/s

answer is C.

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Detailed Solution

i) Mg=udmdt 4000×9.8=500dmdt⇒dmdt=8×9.8=78.4 ii) M(g+a)=udmdt 4000(9.8+9.8)=500dmdt dmdt=8×19.6=156.8kgs−1

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