Question

A rocket with a lift-off mass 20,000kg is blasted upwards with an initial acceleration of 5.0ms^-2. Calculate the initial thrust (force) of the blast.

Answer 1

Mass of the rocket, m = 20,000 kg

Initial acceleration, a = 5 m/s² 

Acceleration due to gravity, g = 10 m/s² 

Using Newton’s second law of motion,

Net force (thrust) acting on the rocket is given by the relation, 

F – mg = ma 

F = m (g + a) 

= 20000 × (10 + 5) 

= 20000 × 15 

= 3 × 10⁵ N

Answer 2

F - 20,000 × 10 = 20000 × 5.0, i.e. 

F = 3.0 × 10⁵N