Final answer:
The combined speed of a 40,000 kg freight car (initially at 5.0 m/s) after it collides with a 30,000 kg stationary car is calculated using the conservation of momentum, resulting in a combined speed of 2.857 m/s.
Step-by-step explanation:
The subject of the question is Physics, and it is related to the conservation of momentum during a collision where two freight cars couple after impact. To find the combined speed after the collision, we can use the law of conservation of momentum. This law states that the total momentum before the collision is equal to the total momentum after the collision, provided there is no external force acting on the system.
Let's denote the mass of the first car as m1 = 40,000 kg and its velocity as v1 = 5.0 m/s. The second car has mass m2 = 30,000 kg and is initially stationary, meaning its velocity v2 = 0 m/s. After the collision, the two cars move together with a combined mass m1 + m2 and a new velocity, v, which we need to calculate.
To compute the combined speed, we set the total momentum before the collision equal to the total momentum after the collision:
(m1 * v1) + (m2 * v2) = (m1 + m2) * v
(40,000 kg * 5.0 m/s) + (30,000 kg * 0 m/s) = (40,000 kg + 30,000 kg) * v
200,000 kg·m/s = 70,000 kg * v
v = 200,000 kg·m/s / 70,000 kg
v = 2.857 m/s
Therefore, after the impact, the combined speed of the two freight cars is 2.857 m/s.