A rocket of mass 100 kg burns 0.1 kg of fuel per sec. If velocity of exhaust gas is 1 km/sec, then it lifts with an acceleration of

dmdt=0.1kg/sec; Mass of the rocket =100kg u=1km/sec=1000m/sec.F=d(mu)dt=mdudt−udmdt=0as the mass is decreasing 100a−1000×0.1=0a=+1m/s2