# 3 Cars Meets Newtons Second Law

by valeriee
Tags: cars, meets, newtons
 P: 1 This is not a homework problem - I am trying to understand the physics of something that happened to me. Scenario: two cars are stopped at a red light. Car #1 in front, and behind it is car #2. Car #3 comes up from behind, does not stop, and hits car 2, and car 2 in turn hits car 1. I am guessing that #3 hitting #2 follows f=ma. But what happens when car #1 is thrown into the mix? I am again guessing that car #1 is following the f=ma from the hit from car #2, but what happens to the forces put on #2 when it is hit from behind, then also gets the force from the impact from the front (from hitting car #1)? Does car #2 just end up getting f=ma twice, once from behind and once from the front? How is this related to the classic egg drop experiment, when you drop the egg on a pillow it doesn't crack but you drop in on a cement floor and it breaks? And one other thing for all you car experts - I've heard there is something called a crumple zone where part of the force of the impact is distributed through the body of the car. How much force is this able to absorb - a lot? A little?
 PF Gold P: 328 Welcome to the Forum! Yes it will get bashed up front and rear. How it relates to an egg dropped on a cushion depends on how much energy can be lost in the collision through processes other than the cars crumpling. So the bumpers might give way first and save the chassis. Also If you have an airbag it will help to save your head shell (skull) in the impact from the rear and the headrest will do the same in the impact to the front.

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