Question

a bullet leaves a rifle with a velocity of 100 m/s and the rifle of mass 2.5kg recoils with a velocity of 1 m/s. find the mass of the bullet.

Answer 1

According to conservation of momentum
m1v1 = m2v2
m1 = m2v2 / v1
m1 = (2.5 * 1) / 100
m1 = 0.025kg
m1 = 25g

Mass of bullet is 25g