Comments on: Timeline of a Car Crash

By: x

Mon, 04 Jan 2010 05:39:01 +0000

i am really speechless. the breakdown you presented is really scary and will certainly have it in mind when i am driving….. thanks for sharing it.

By: James

James — Thu, 29 Oct 2009 16:49:09 +0000

All that happens before the passenger even realises. wow!

By: Emtucifor

Emtucifor — Tue, 08 Sep 2009 17:08:33 +0000

My apologies. I should have used the word energy instead of force.

By: T F

T F — Sat, 29 Aug 2009 20:33:20 +0000

Well done

All learner drivers should know this

Thanks for sharing

By: Bob

Bob — Sun, 26 Jul 2009 12:43:52 +0000

Emtucifor>>> Force = mass * ACCELERATION

By: Orlandin

Orlandin — Wed, 22 Jul 2009 13:56:04 +0000

The reason that most crashes are tested around 30 mph, is the fact that beyond that, your chances of survival diminish quickly. An airbag can only deploy so fast before it is considered a hazard instead of a saving point. The 30 to 35 mph rule also comes from the fact that most cities have a city wide 35 mph speed limit unless otherwise posted.

By: Emtucifor

Emtucifor — Thu, 16 Jul 2009 05:18:10 +0000

>> and if it was a SMALLER car, you’d push it backward.

Please read between the lines as I obviously can’t avoid silly mistakes. :)

By: Emtucifor

Emtucifor — Thu, 16 Jul 2009 05:16:33 +0000

Er, “directly correlates to its speed and nothing else” >> I wasn’t ignoring force = mass x velocity here, but trying to say that the wall doesn’t have anything to do with the force the car experiences.

By: Emtucifor

Emtucifor — Thu, 16 Jul 2009 05:15:14 +0000

You guys are thinking about the 2 cars going 30 mph toward each other incorrectly. Stop trying to add speed and think about force.

What deceleration does a 30mph car undergo when it hits a solid unmovable wall? It decelerates to 0mph in effectively 0 space (yes, it crumples, but the point is that the front bumper stops nearly instantly and then the rest of the car crushes and comes to rest behind it). The force it experiences directly correlates to its speed and nothing else.

Now if you propel a ball at the wall at 30mph, it rebounds with a certain force. Now make the same throw but remove the wall and have a friend throw an identical ball #2 from the other direction so they exactly collide where the wall used to be. How fast would ball #2 have to be traveling to make ball #1 undergo the exact same rebound and force as with the wall? Obviously, it would have to be going exactly 30 mph.

See, the wall resists a 30mph crash of a 4000-pound car with exactly the force applied to it: a 30 mph crash of a 4000-pound car. A heavier car traveling faster will hit with more force, but it will resist with that force.

So I hope you can see now that the only speed an identical opposing car can be traveling to simulate crashing with a solid wall is: exactly the same speed.

Another way to look at it: if you were in motionless in outer space and you threw a wrench, you would be propelled backwards (or spin yourself, but set that aside for now). If you turned exactly around and then caught a new wrench that was sailing toward you at the same speed you’d thrown the first wrench, you’d come exactly to a stop. Hitting an identical car coming toward you is a bit like “catching” it and coming to an exact stop. The force is exactly enough to make you stop. If it was a bigger car, you’d get pushed backward after impact, and if it was a larger car, you’d push it backward.

In fact, it would probably be less deceleration forces on your body to hit a car instead of a wall: the cars could interpenetrate or slip to the side or above/below and thus decelerate over a greater distance, reducing the force on you.

By: Rick

Rick — Tue, 30 Jun 2009 15:16:02 +0000

@KK That is incorrect. The cars are approaching each other at a relative speed of about 60 mph, if both are going 30mph toward each other.

So both cars’ initial collision experience will be about 60 mph.