Question 135: Laws of Motion

Question

The initial mass of a rocket is 1000 kg. Calculate at what rate the fuel should be burnt so that the rocket is given an acceleration of 20 ms
-2
. The gases come out at a relative speed of 500 ms
$$-$$1
with respect to the rocket : [Use g = 10 m/s
2
]

Accepted Answer

$${F_{thrust}} = \left( {{{dm} \over {dt}}.{V_{rel}}} ight)$$
$$\left( {{{dm} \over {dt}}{V_{rel}} - mg} ight) = ma$$
$$ \Rightarrow \left( {{{dm} \over {dt}}} ight) 	imes 500 - {10^3} 	imes 10 = {10^3} 	imes 20$$
$${{dm} \over {dt}}$$ = (60 kg /s)

Answer

6.0 $$	imes$$ 10
2
kg s
$$-$$1

Answer

500 kg s
$$-$$1

Answer

10 kg s
$$-$$1

Answer

60 kg s
$$-$$1

Laws of Motion

The initial mass of a rocket is 1000 kg. Calculate at what rate the fuel should be burnt so that the rocket is given an acceleration of 20 ms -2 . The gases come out at a relative speed of 500 ms $-$1 with respect to the rocket : [Use g = 10 m/s 2 ]

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