Q4. A machine gun fitted on a trolley of mass 2000 kg on a horizontal frictionless surface. If the gun fires bullet each of mass 10 gm with a velocity of 500 m/s with respect to the trolley and if the number of bullet fired per second is 10 then calculate the average thrust exerted by ejected bullet on the system.

- The average thrust exerted by ejected bullet is nothing but the momentum gained by that bullet when fired.

- Momentum can be understood as a force or an energy gained by a moving object.

- This force is given by F = mv (mass and velocity of bullet). 

- But the number of bullets per second also amplifies this momentum, therefore, the force in this case is expressed as F = n x mv ('n' is   the number of bullets)

- Converting the mass of a bullet in kilograms we get m=0.010 kgs.

- Check if all the units involved either belong to the SI (prefered) or CGS system.

- Substituting the values of m,v and n in the above formula for 'F' we get,

  F = 10 x 0.010 x 500 = 50 N