Question

A Diwali rocket is ejecting 0.05 kg of gases per second at a velocity of 400 ms${}^{-1}$. The accelerating force on the rocket is

• A. 20 dyne
• B. 20 newton
• C. 20 kg wt
• D. sufficient data not given

Answer 1

Answer: (B)

20 newton

Rate of ejecting gasses $\frac{dm}{dt}=0.05kg/s$

Velocity of ejecting gasses $v=400m/s$

Thus accelerating force $F=\frac{dm}{dt}v$

$⟹$ $F=0.05\times 400=20N$