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A man fires the bullet of mass m each with a velocity v from a machine gun. If he fires n bullets every second, the reactional force per second on the man will be

\[(a)\;\frac{m}{v}n \quad (b)\;mnv \quad (c)\;\frac{mv}{n} \quad(d)\;\frac{vn}{m} \]

1 Answer

Answer: mnv
Per Newton's second law, $F = \large\frac{dp}{dt} $
Total mass of bullet fired in 1 second$= m \times n$
$\Rightarrow$ Change in momentum per second $dp =p_2 - p_1 = mnv-0$
$\Rightarrow F = \large\frac{mnv - 0}{1}$$ = mnv$
answered Jul 4, 2013 by meena.p
edited Aug 20, 2014 by balaji.thirumalai

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