# A railroad car with a mass of 30,000 kg is moving at 2.0 m/s when it runs into an at-rest freight car with an equal mass. The cars lock together. What is their final velocity?

QUESTION POSTED AT 01/06/2020 - 03:35 PM

QUESTION POSTED AT 01/06/2020 - 03:35 PM

The total momentum of the system is preserved through the collision.

Note that momentum is

P = m*v

where m = mass

v = velocity.

Initial momentum:

P1 = (30000 kg)*(2 m/s) = 60000 (kg-m)/s for the moving car

P2 = 0 for the starionary car.

Final momentum:

P3 = (30000 + 30000)*v = 60000v (kg-m)/s

Because momentum is preserved,

P3 = P1 + P2

60000v = 60000

v = 1 m/s

The final velocity is 1 m/s.

Answer:**1.0 m/s**

Note that momentum is

P = m*v

where m = mass

v = velocity.

Initial momentum:

P1 = (30000 kg)*(2 m/s) = 60000 (kg-m)/s for the moving car

P2 = 0 for the starionary car.

Final momentum:

P3 = (30000 + 30000)*v = 60000v (kg-m)/s

Because momentum is preserved,

P3 = P1 + P2

60000v = 60000

v = 1 m/s

The final velocity is 1 m/s.

Answer:

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