[jakeogh]

Excellent! They are generally safer.

Newton's 2nd law:

F1 = -F2

m1a1 = -m2a2 (1)

The longer distance that big vehicles have between people and hard surfaces is a good thing; modern airbags are amazing.

1) glossing over details, because of the way materials scale, this works out (for a smaller human a) even with larger m's on both sides, because there are longer distances involved, and therefore longer crush zones, and more room between humans and hard surfeces for airbags to fill. In accidents that involve a vehicle and a immovable object, this also works out better.

Small vehicles are inherently unsafe, and should come with a disclamer tutorial on basic dynamics.

[seszett]

> Small vehicles are inherently unsafe, and are primarly marketed to people who dont know basic dynamics.

Or to people who need to park their car in a city. Or who rarely have to drive over 50 km/h. Or who can't afford a larger car.

There really are a lot of reasons for having a smaller car, it's quite ingenuous to chalk it up to "not knowing basic dynamics".

[jakeogh]

Staying alive is more important. Larger cars are not significantly more expensive; people get to choose, some ride motorcycles, it's their choice, but we shouldnt gloss over the 2nd law. Unfortunatly F=ma is not common knowledge. Pointing that out shouldn't be offensive. When one learns that simple rule, they apply it. You quoted when I was still editing, first versions are always worse:)

[wcoenen]

I think the more relevant equation is a=𝚫v²/(2d) which gives you the acceleration needed to realize a speed change 𝚫v over a distance d. Larger cars allow for a larger d, therefore a smaller peak acceleration in crashes.

edit: I just realized you were focusing on mass. While a higher mass is safer for you, it comes at the cost of making things less safe for everyone else. Making cars larger while keeping mass the same doesn't come with this trade-off, it reduces peak acceleration for everyone.

[jakeogh]

To your edit: yes, that's what "The longer distance that big vehicles have between people and hard surfaces is a good thing" means.

Larger (modern) vehicles do weigh more; car density does not change much, I would be interested if there is a counter example to that.

[jakeogh]

Yes, max(a) is the thing to minimize, but to explain it I think starting with the F=ma symmetry is more intuitive, and then point out why d matters.