Q2 of 35 Page 143

A bullet of mass 20kg is fired horizontally with a velocity of 150m/s from a pistol of mass 2kg. Find recoil velocity.


Mass of bullet = 20kg


Mass of pistol = 2kg


Velocity of pistol= 150m/s


Let, m1 = 20kg


m2 = 2kg


u1 = 0m/s


u2 = 0m/s


v1 = 150m/s


v2 =?


According to Law of Conservation of Momentum,


Initial Momentum = Final Momentum


m1u1 + m2u2 = m1v1 + m2v2


(20kg × 0m/s) + (2kg × 0m/s) = (20kg × 150m/s) + (2kg × v2)


0 = 3000 + 2v2


–1500m/s = v2


NOTE: Negative sign denotes that pistol moves opposite to that of the bullet.


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