You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!
The banners on the left side and below do not show for registered users!
If you have any problems with the registration process or your account login, please contact contact us.
Mythbusters crew decided to revisit an old myth that was drawing the ire of the show's fans for quite some time. And it's sure to be an interesting topic to automotive enthusiasts.
When two cars collide, each traveling 50 miles per hour, does the resulting force equal one car hitting an immovable object at 100 miles per hour?
It seems like such simple physics, no? But don't forget Newton's third law. To quote the great Wikipedia of knowledge, "Whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction." Or, more simply, for every action there is an equal and opposite reaction.
Advertisement
Last edited by SkinnyPupp; 05-08-2010 at 11:33 AM.
Reason: replaced link with video embed
You can find the answer to that solution with a couple of energy and momentum questions.
An object moving at 100mph/kph has 2x the energy of 2 objects moving at 50mph/kph (units are arbitrary if you are using the same ones for comparison).
If vehicles were static objects then this would be true.
Actual testing has shown that the average of head on collisions in the real world (both cars at highway speeds of 100 km/h) produces forces equivalent to a single object coming to a dead stop at <70 km/h, not 200 km/h.
You have to take into account the amount of energy absorbed by the crumple zones of the vehicle, and no simple equation is going to tell you that.
This is why, even with advanced computer simulations, manufacturers still go ahead and actually crash cars to measure real world results.
the problem with the misconception is that they are forgetting that 2x amount of energy working on 2x amount of mass makes equivalent of 1x the energy working on 1x of mass.
The lime yellow Korean crap car has seen its fastest acceleration to 100mph ever in its life pulled by the two V8 engines.
__________________ ⇐ If I bothered replying, that's the face I made while I typed.
Yeah, it's physics 101. The force calculation isn't wrong. There's the same amount of force equating to 2x of the impact speed. They just forgot to add 2xmass in there.
If Object B is moving 2x as fast as Object A when slamming into a stationary wall, there is 4 times the energy. Physics also shows that the acceleration (and therefore the force) is 4x for Object B given the same displacement (ie crumple zone for the car).
The reason why manufacturers still crash-test vehicles is not that it's too hard to predict things that shatter, as well as predicting the behaviour of fluids (eg gas in the gas tank). In addition no real-world collision ever happens on a perfectly flat piece of land, there might be some manufacturing flaw or rust in the car frame etc. They've made huge strides over the years but it's still way too computationally complex. Anyone who's taken CFD will know what I'm talking about.
You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!
The banners on the left side and below do not show for registered users!
mythbusters. 
