Answer:
The speed of the car immediately after the boulder is dropped = 8.696 m/s
Explanation:
Newton's Third Law Of Motion: Its states that to every action there is an equal and opposite reaction.
From Newton's third law of motion,
The momentum of the empty train car before the boulder dropped = momentum of the train car after the boulder is dropped.
But Momentum = mass × Velocity.
m₁u₁ = m₂u₂ ................................. Equation 1
Making u₂ the subject of the equation,
u₂ = m₁u₁/m₂................................ Equation 2
Where m₁ = mass of the empty train car, m₂ = mass of the train car and the boulder, u₁ = velocity of the train car before the boulder is dropped, u₂ = velocity of the train car after the boulder is dropped.
Given: m₁ = 20000 kg, m₂ = 20000 + 3000 = 23000 kg, u₁ = 10 m/s.
Substituting these values into equation 2,
u₂ = (20000 × 10)/23000
u₂ = 8.696 m/s
Therefore the speed of the car immediately after the boulder is dropped = 8.696 m/s
