Question

At a certain instant of time the mass of a 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

• A.
• B.
• C. $2 m / s ^ { 2 }$
• D. $1 m / s ^ { 2 }$

Answer 1

Answer: (B)

Answer 2

The acceleration of a rocket is given by

$a = \frac { v } { m } \left( \frac { \Delta m } { \Delta t } \right) - g = \frac { 400 } { 100 } \left( \frac { 5 } { 1 } \right) - 10$ $= ( 20 - 10 ) = 10 \mathrm {~m} / \mathrm { s } ^ { 2 }$