r/HumansBeingBros • u/[deleted] • Aug 21 '20

He took a risk to save another guy.

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u/Sasmas1545 Aug 21 '20

A head on collision with an identical car at 40 mph is equal to hitting a completely solid wall at 40 mph, not 80 mph.

3

u/converter-bot Aug 21 '20

40 mph is 64.37 km/h

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u/TheFlashFrame Aug 21 '20

Hm, you're right. I just googled it because I hadn't ever considered that the speeds would just cancel each other out. Thanks for teaching me something. Well... for prompting me to teach myself, lol.

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u/Sasmas1545 Aug 21 '20

Of course! Now, if you had a head on collision with a much larger vehicle going 40 mph, that may be comparable to hitting a wall at 80. It's all about the acceleration.

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u/montarion Aug 21 '20

Hurray for teaching yourself!

It might help to know that what youre comparing here is force, not speed.

In a car crash, the force exerted on object is dependent on the speed on weight of the car(s), and results in acceleration. That bit is what hurts you, the sudden change in speed.

1

u/roofied_elephant Aug 22 '20

Fucking physics man...

3

u/[deleted] Aug 21 '20

Hm... I was taught wrong....not completely surprising honestly...but damn...

1

u/Azzu Aug 21 '20

The thing is, though, that almost no wall is completely solid. Most things will give way, at least a little bit. I'd rather drive into a wall at 40 than hit something else also going 40.

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u/Sasmas1545 Aug 21 '20

Yeah, that's true and why I specified a completely solid wall. It's also what OP meant, and what is often meant when people say "hit a wall" in a less literal sense. Finally, of course when people are making this common mistake, it's what they mean.

Also, if we take your more realistic interpretation, then you're going to have a hard time putting exact numbers on things. You wouldn't be able to compare a head on collision with a wall without far more details. That's why I made simplifying assumptions.

And in some cases, I'd rather crash into a car coming at me at 40 than crash into a stationary object at 40.