A diwali rocket is ejecting 0.05 kg of gases per second at a velocity of 400 m s -1 . The accelerating force on the rocket is

( a ) 20 dyne ( b ) 20 newton

( c ) 20 kg wt ( d ) sufficient data not given

We have,

dm/dt = 0.05 kg/s

v = 400 m/s

We know,

P = mv

=> dP/dt = d(mv)/dt = v(dm/dt) + m(dv/dt)

=> F = v(dm/dt) + 0

=> F = (400)(0.05)

=> F = 20 N

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