Question

A body of mass 5 kg moving with a velocity 3 m/s
collides with another body of mass 3 kg at rest. After
collision, both move with the same velocity. Find
their common velocity.​

Answer 1

3 m/ s is the right answer because of conservation of momentum

Answer 2

mass of body 1 = 5kg

initial velocity (u) = 3 m/s

final velocity (v) = v

mass of body 2 = 3kg

initial velocity (u) = 0 (at rest)

final velocity (v) = v

m1 u1 + m2 u2 = m1 v1 + m2 v2

5×3 + 3×0 = 5×v + 3×v

15+0 = 8v

v = 15/8

v = 1.88 m/s