Nick Lane's book is certainly interesting. He takes time to tell me what he's going to say later, which is nice. ("say what you are going to say, say it, then repeat what you said" model)
But at page 89 he writes, regarding flowing water: "Funnel the flow into a confined channel and its force increases"
Mmm, f=ma. A narrow channel *reduces friction*, increasing the *net* acceleration. The cross section isn't magic- make it too narrow and it increases friction. I'd be more comfortable with a two-step explanation about friction reducing net acceleration. Am I just being a jerk and don't "get" it?
Thanks,
Bill
For context, I did, eventually, follow for 4, equal-legged, right triangles with their hypotenuses forming a square, at 45 degrees to the external square outlined by the 4 right-angled, shorter sides. Helpfully annotated, "Behold!". I can mentally flip the outer triangles across the hypotenuses, proving hypotenuse squared = 2 x ((equal side) squared) This wordless proof attributed to Bhāskara II (c. 1114–1185), for the Pythagorean theorem.
But the popular version, with the 4 hypotenuses forming an outer square, with the triangles having dissimilar sides, and an inner square of (difference between long and short sides)^^2 doesn't speak to me. Illustrating why I flunked both Physics and Thermo, and did poorly on the theoretical part of O-chem. As Clint Eastwood says, "A man's got to know his limitations".