What happens if I have an extra person in my car?

What happens to a person when they are hit by a car going 40 miles an hour?

• I'm just doing a project in school, and I'd like to know what the major difference is between getting hit by a car that's going 30 miles per hour, and a car that's going 40. The thing I really want to know is if 10 miles per hour makes a difference in impacts-could someone survive just because of that 10 miles per hour? Also, if the laws of physic actually play a part. Y'know, "every force has an equal and opposite force"? Or if the energy caused by the impact is absorbed by the person who is hit. Answers greatly appreciated!

• Answer:

  "Also, if the laws of physic actually play a part. Y'know, "every force has an equal and opposite force"? Or if the energy caused by the impact is absorbed by the person who is hit." The car as a large mass. A person has a small mass. When a large mass collides into a stationary small mass, the large mass will continue moving (at a slightly slower speed) while pushing the small mass. This is assuming there is no friction, but with such a mass different, the outcome should be close anyways. The equation would be: momentum = velocity * mass so... (velocity before the crash) * (car's mass) = (unknown new velocity after the crash) * (car's mass + human mass) I'm pretty sure both crashes will kill you, but the 30mph car has a better chance of stopping before the crash (if the driver is fast with using the brakes).