Question

A PSLV rocket burns 0.5 kg of fuel per second and ejects out a gas with a velocity of 15 kms^-1 . In this case the thrust provided by PSLV will be ______. 
1. 1.5 kN
2. 7.5 kN
3. 1.5 kJ
4. 7.5 kJ

Answer 1

Correct Answer - Option 2 : 7.5 kN

CONCEPT:

Newton’s Second Law:

• The rate of change of linear momentum of a body is directly proportional to the external force applied on the body and this change takes place always in the direction of the applied force.
• If a body of mass m moves with velocity \(\vec v\) then its linear momentum can be given by \(\vec p = m\vec v\) and if force \(\vec F\) is applied on a body, then
  \(\therefore \vec F = m\vec a\)
  Where F = Force, m = mass  and a = acceleration

CALCULATION:

Given – Mass of a object (m) = 0.5 kg, velocity/time (u/t) = 15 km/s-1 = 15 × 103 m/s-1 

• According to Newton’s second law of motion,

\(⇒ F = m(\frac{u}{t})\)

\( ⇒ F = 0.5\times 15\times10^3 = 7.5\times 10^3\, N=7.5\, kN\)