The Physics of Car Crashes

How is the chemical energy of gasoline transformed into kinetic energy of a moving car? And where does that kinetic energy go when the car crashes into something and stops moving?

And twitter - @minutephysics

Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute! Created by Henry Reich

[DerozH]

“Speed has never killed anyone. Suddenly becoming stationary, that's what gets you.”
― Jeremy Clarkson

[ainoakeisari]

This is really cool. A good way to counter the people who say that "cars were better back in the day"

[EugeneKhutoryansky]

Crunchiness is something that good cars and good candy bars have in common.

[KishoreShenoy]

Doing a joke about petrol would be fuelish

[battmarn]

this is why the tesla model S has such a good safety rating. with no engine in the way, the entire front section is a huge crumple zone

[uceid]

I liked the part about how inneficient fuel engines are... that's crazy.

[drmaudio]

Your last point is excellent. A dent or crease in the wrong place can dramatically reduce the yield strength of that component, thus reducing it's ability to absorb that crash energy.

[antivanti]

Another technique is that the engine is designed to be deflected down under the safety cell. This is good for 2 reasons. The first is that the engine is pretty solid and can't be compressed. The second is that the engine is heavy but by deflecting it down under the car it doesn't have to decelerate gently and the crumple zones don't need to worry about absorbing all that energy. Let the engine hit the tree and come to a dead stop while the car is "gently" decelerated by the crumpling above it.

[DrRChandra]

If I understand you correctly, although dings and dents might be aesthetically unpleasant, it's important to get them repaired anyway, because some of the part's energy absorbing (crushing) ability has been removed from the part, thus compromising its ability to absorb energy through crushing in subsequent collisions.

[blinkyrob]

Fantastic stuff Henry. I'll show this to my classes after Christmas when we're preparing for exams!

[Gytax]

A new car built by my company leaves somewhere traveling at 60 mph. The rear differential locks up. The car crashes and burns with everyone trapped inside. Now, should we initiate a recall? Take the number of vehicles in the field, A, multiply by the probable rate of failure, B, multiply by the average out-of-court settlement, C. A times B times C equals X. If X is less than the cost of a recall, we don't do one.

[benjaminhersh]

I love watching your videos and while working on my driving school, this video showed up and made my class so much better! Keep up the amazing content ❤❤❤

[limors]

I think this is one of the most informative videos I've watched here, I had no idea that the front of the car does that. New appreciation to it.

[Nibooss]

Oh, thanks for uploading this 4 days before my driving test. :D

[akoso]

Do you know what I like more than crashing cars....?


KNOWLEDGE

[leoncampa]

You should have added the purpose of airbags, which are also designed to decelerate your body vs the car.

What is often mistakenly assumed is that airbags are soft cushions that hit your face, but if that were the case, they would shred apart from the explosion and your face would be hit by a huge amount of shrapnel from the airbag's micro-explosion.

Instead, airbags are actually made of a material that is similar to a basketball so that they could withstand the pressure of the sudden inflation, and when they hit you in the face, it really feels like a basketball thrown right into your nose.

[agnestaylor]

I thought it takes 5 teaspoons of sperms to power a car...*facepalm*

[Dip_Physics]

Ah very informative. It is astonishing to know what level of engineering and Physics goes into making cars and other machines of our daily lives. Thanks for such a nice video.

[AndrewHallcomedy]

This helped dispel the myth that older cars (being an older guy I remember those old "solid" cars) are safer than the newer, lighter vehicles. Sharing this!

[daedra]

...and this video is epitome of why we love physics.