Question

3.3.2 test (cst): forces
question 17 of 20
engineers are using computer models to study train collisions to design safer train cars. they start by modeling an elastic collision between two train cars traveling toward each other. car 1 is traveling north at 20 m/s and has a mass of 12,745 kg. car 2 is traveling south at 15 m/s and has a mass of 4,125 kg. after the collision, car 1 has a final velocity of 3 m/s north. what is the final velocity of car 2?
a. 38 m/s north
b. 38 m/s south
c. 56 m/s south
d. 56 m/s north

Explanation:

Step1: Set up the conservation of momentum formula

The conservation of momentum formula is \(m_1v_{1i}+m_2v_{2i}=m_1v_{1f}+m_2v_{2f}\). Let north be the positive direction. So \(m_1 = 12745\space kg\), \(v_{1i}=20\space m/s\), \(m_2 = 4125\space kg\), \(v_{2i}=- 15\space m/s\), \(v_{1f}=3\space m/s\).

Step2: Substitute the values into the formula

$$
LATEXBLOCK0
$$

Since \(v_{2f}>0\), the direction is north.

Answer:

A. 38 m/s north