Question

A freight train car with a mass of 1.2 × 104 kilograms, travelling with a velocity of 23 meters/second, collides with a stationary freight train car of equal mass. What is the momentum of the system after the collision?

A. 1.2 × 105 kilogram meters/second
B. 1.4 × 105 kilogram meters/second
C. 2.4 × 104 kilogram meters/second
D. 2.8 × 105 kilogram meters/second

Answer 1

D. 2.8×10⁵ kg·m/s

Step-by-step explanation:

You want the momentum of the system after the collision of a 1.2×10⁴ kg freight car with a velocity of 23 m/s and a stationary car of equal mass.

Momentum

The total momentum of the system will be conserved through the collision. This means the final momentum is the same as the initial momentum:

momentum = m1·v1 +m2·v2 = (1.2×10⁴ kg)(23 m/s) + (1.2×10⁴ kg)(0 m/s)

momentum ≈ 2.8×10⁵ kg·m/s . . . . . matches choice D