A rocket with a lift-off mass 20,000 kg is blasted upwards

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

solution:

Mass of the rocket, m = 20,000 kg

Initial acceleration, $a=5 \mathrm{~m} / \mathrm{s}^{2}$

Acceleration due to gravity, $g=10 \mathrm{~m} / \mathrm{s}^{2}$

Using Newton’s second law of motion, the net force (thrust) acting on the rocket is given by the relation:

F – mg = ma

F = m (g + a)

= 20000 × (10 + 5)

$=20000 \times 15=3 \times 10^{5} \mathrm{~N}$

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