Why does kinetic energy increase quadratically, not linearly, with speed? (2011)

Post by davidivadavid » Sat, Jun 27, 2026, 1:24 AM UTC

joshAg wrote: post #27

davidivadavid wrote: post #7

Earlier quoted context omitted.

More than twenty years ago, I quit a program that taught math/cs/physics (the notorious French "classes préparatoires") ~almost precisely over this: I felt like I was being taught physics like it was an axiomatic system where the tricks should not be questioned, they just work so "shut up and calculate" (and you don't even need to be doing quantum mechanics for that). I just felt like we never got to the heart of the…

Your issue with physics but not with math reminds me a little of Hume's law. The difference that has always made that difference "make sense" to me is that math rules, even the axiom we use, are entirely chosen by the people using them, but the rules of physics are only useful if they match/predict what happens in the real world. For math we get to pick the ones that happen to be useful at a given time for a given pr…

Post by joshAg » Sat, Jun 27, 2026, 1:32 AM UTC

davidivadavid wrote: post #31

joshAg wrote: post #27

Earlier quoted context omitted.

Your issue with physics but not with math reminds me a little of Hume's law. The difference that has always made that difference "make sense" to me is that math rules, even the axiom we use, are entirely chosen by the people using them, but the rules of physics are only useful if they match/predict what happens in the real world. For math we get to pick the ones that happen to be useful at a given time for a given pr…

I think what it boils down to is that in my experience physics education lacks a clear historical component about how the current state of the art is a gradual process of proposing new models and rejecting old ones and figuring out the gaps between reality and the model. Instead, it feels like a God-given set of equations (that lots of people consider "the truth" for some reason), that you apply to cookie-cutter prob…

Post by symian » Sat, Jun 27, 2026, 1:38 AM UTC

Agingcoder wrote: post #4

Physics is an endless source of frustration to me. It feels like a mix of random tricks, most of which I don’t understand. I find math and compsci reasonably understandable, can read research papers in both fields ( and have published papers) etc. There’s something specific about physics I don’t get but I’ve never been able to figure out what. The main symptom is that most cause -> consequence in such demonstrations…

Post by elromulous » Sat, Jun 27, 2026, 1:44 AM UTC

BigTTYGothGF wrote: post #20

tracerbulletx wrote: post #18

Earlier quoted context omitted.

But what if the cars are spherical cows?

Cows can't roll that fast.

Post by linzhangrun » Sat, Jun 27, 2026, 1:45 AM UTC

throw0101a wrote: post #2

Fun little anecdote: A blue care is travelling along at 70 units, and a red car (exact same make and model) is catching up to it going 100. When they're both right beside each other a bend in the road reveals an obstacle blocking both lanes, so both cars brake at the same intensity and deceleration. The blue care stops right before the obstacle. Since the red car was going at a faster speed, and braked at the same ra…