Question

Two students in bumper cars want to prove conservation of momentum. They collide their bumper cars. The first bumper car has a mass of 120 kg
and was moving with a velocity of 4.0 m/s
before the collision and with a velocity of −2.0 m/s
after the collision. The second bumper car has a mass of 90 kg
and was moving at a velocity of −5.0 m/s
before the collision. To prove conservation of momentum, what must the velocity of the second bumper car be after the collision?(1 point)
Responses

3.0 m/s

3 point 0 meters per seconds

2.7 m/s

2 point 7 meters per seconds

2.3 m/s

2 point 3 meters per seconds

1.0 m/s

Answer 1

Use conservation of momentum:

Initial momentum = 120(4.0) + 90(−5.0) = 480 − 450 = 30 kg·m/s.

After collision: 120(−2.0) + 90 v2f = 30 → −240 + 90 v2f = 30 → 90 v2f = 270 → v2f = 3.0 m/s.

Answer: 3.0 m/s.