Answer:
12 kg
Explanation:
Momentum before collision = momentum after collision
m₁ u₁ + m₂ u₂ = m₁ v₁ + m₂ v₂
After the collision, they have the same velocity, so v₁ = v₂ = v:
m₁ u₁ + m₂ u₂ = m₁ v + m₂ v
m₁ u₁ + m₂ u₂ = (m₁ + m₂) v
We know that m₁ = 6 kg, u₂ = 0 m/s, and v = u₁ / 3.
(6 kg) u₁ + m₂ (0 m/s) = (6 kg + m₂) (u₁ / 3)
(6 kg) u₁ = (6 kg + m₂) (u₁ / 3)
6 kg = (6 kg + m₂) (1/3)
18 kg = 6 kg + m₂
m₂ = 12 kg
