Question

Two objects, each of mass 1.5 kg are moving in the same straight line but in opposite directions. The velocity of each object is 2.5 m s⁻¹ before the collision during which they stick together. What will be the velocity of the combined object after collision?

Answer 1

Mass of one of the objects, m₁ = 1.5 kg

Mass of the other object, m₂ = 1.5 kg

Velocity of m₁ before collision, v₁ = 2.5 m/s

Velocity of m₂, moving in opposite direction before collision, v₂ = −2.5 m/s

(Negative sign arises because mass m₂ is moving in an opposite direction)

After collision, the two objects stick together.

Total mass of the combined object = m₁ + m₂

Velocity of the combined object = v

According to the law of conservation of momentum:

Total momentum before collision = Total momentum after collision

m₁v₁ + m₂ v₂ = (m₁ + m₂) v

1.5(2.5) + 1.5 (−2.5) = (1.5 + 1.5) v

3.75 − 3.75 = 3 v

v = 0

Hence, the velocity of the combined object after collision is 0 m/s.