Question

A rocket with a lift-off mass 20,000 $\text {kg}$ is blasted upwards with an initial acceleration of 5.0 $\text \,m \text s^{-2}$. Calculate the initial thrust (force) of the blast.

Answer 1

Mass of the rocket, $\text m$ = 20,000 $\text {kg}$
Initial acceleration, $\text a$ = 5 $\text m/\text s^2$
Acceleration due to gravity, $\text g$ = 10 $\text m/\text s^2$
Using Newton’s second law of motion, the net force (thrust) acting on the rocket is given by the relation:
$\text F$ – $\text {mg}$ = $\text {ma}$
$\text F$ = $\text m$ ($\text g$ + $\text a$)
$\text F$ = 20000 × (10 + 5) = 20000 × 15 = $3\times 10^5$ N