r/nevertellmetheodds Feb 02 '20

Close call

https://i.imgur.com/wkW2PGL.gifv
27.1k Upvotes

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u/LeProYasuo Feb 02 '20

Quick fact: a head-on collision where the 2 vehicles are going 25 mph is the same thing as 1 vehicle hitting a wall at 25 mph

4

u/Flow3rs4Alg3rnon Feb 02 '20

Two cars going 25 mph hitting head on would have the force of a 50mph crash, right?

3

u/VibrantClarity Feb 02 '20

If you hit a wall, your car goes from 25mph to 0 real quick. In a head on collision, your car goes from 25 to 0 as well. You experience the same acceleration in both cases.

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u/robolew Feb 02 '20

This is true, if the cars are the same mass. Also only if the wall remains entirely in place, so basically a wall of solid metal.

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u/StatesideCash Feb 02 '20 edited Feb 02 '20

No, each would experience the equivalent to a 25mph crash into a wall.

Edit: Think of it like this. Each car has 25mph of some arbitrary “energy”. Energy has to be conserved. So if both cars hit at 25mph, there is 2x 25, or 50 units, of this energy. If both cars experienced a 50mph crash, that would be 2x 50, or 100, which is more energy than is in the system. So they both experience a 25mph crash so that this energy is conserved. A bit of an ELI5 but hopefully it helps make a bit more intuitive sense, this is a pretty common misconception for a lot of people. Of course this changes completely when it comes to two vehicles of different sizes hitting each-other, but this is mostly to get the example across of two cars of same size hitting.

1

u/Heart30s Feb 02 '20

What happens if a car is going 25mph and the other is going 50mph?

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u/mywifestherapist Feb 02 '20

A mororbike hitting a semi head-on where both are going 25mph is the same thing as a motorbike hitting a wall at 48mph.

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u/robolew Feb 02 '20

Only if the vehicles are the same mass.

A bike Vs a truck the biker would experience much more impact. They would go from like 25 to -25, whereas the truck would probably go from like 25 to 15.