Question

A bullet of mass A and velocity B is fired into a wooden block of mass C. If the bullet gets embedded in the wooden block, then the the magnitude of velocity of the system just after collision will be

(a)A+B/AC . (b)A+C/B+C . (c)AC/B+C . (d)AB/A+C

Answer 1

Here,
Mass of bullet = a
Mass of wood = c
Velocity of bullet = b.
Initial momentum of the bullet = ab
Initial momentum of the wood = c×0 = 0 (because the wood was at rest)
Final mass of the system = a + c (because bullet goes inside the wood)
Let the velocity of the system = v
We know that
Initial momentum = final momentum
Initial Momentum of bullet + initial momentum of the wood = final momentum of the system
ab + 0 = (a + c)v
=> v = ab/(a + c)