Laws of motion NCERT Solutions Class 11 Physics - Solved Exercise Question 5.9

Question 5.9:

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

Solution:
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, the 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