Q. At a certain instant of time the mass of rocket going up vertically is 100 kg. If it is ejecting 5 kg of gas per second at a speed of 400 m/s, the acceleration of the rocket would be (Taking $g = 10\ m/s^{2})$
A) $20\ m/s^{2}$
B) $10\ m/s^{2}$
C) $2\ m/s^{2}$
D) $1\ m/s^{2}$
Explanation
(b) The acceleration of a rocket is given by
$a = \frac{v}{m}\left( \frac{\mathrm{\Delta}m}{\mathrm{\Delta}t} \right) - g$
$= \frac{400}{100}\left\lbrack \frac{5}{1} \right\rbrack - 10$
$= 20 - 10 = 10\ {m/s}^{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.