Originally Posted by
kbarch
Ever hear of momentum?
My point about mechanics is that it is not as simple, or as completely understood, even by educated people, even for simple matters, as you suggest.
Momentum is actually irrelevant for this discussion. Conservation of energy is all that is needed.
For instance, it would seem a simple thing to do to determine the velocity of a dropped ball falling to earth through air, but try determining it with basic high school physics. Try determining how long it will take to fall to the earth if dropped from an airplane, and where. As it happens, all the maths required to figure out that seemingly simple problem weren't clear and complete until the 1800s. If mechanics were as simple as you suggest, I'm sure we would have figured out how to make such basic determinations a long time before. It's just a dumb ball falling straight down, right?
You have again implied that because a problem would have been difficult to analyze 200 years ago, it is somehow still difficult to analyze today. This is not a difficult problem to analyze. I know (literally) dozens of people who can analyze this problem in less time than its taking me to type this response.
Compare that to the movement of our legs on a bike. High school physics only provides a partial explanation of the phenomenon of the action of the pedals - it does not even begin to describe the activity in our legs as we spin them. Insistence that it does is a gross oversimplification, and the insistence that our limbs have no elasticity is contrary to basic anatomy and human kinetics.
It doesn't matter if high school physics can or cannot describe the exact motion of the pedals, because conservation of energy is all that is needed to refute your original premise. You also don't have to describe the activity in the legs in detail; all you have to know is that movement of the legs is impossible without the expenditure of energy.
You did not respond to my previous questions:
Have you ever had a high school physics class? Anything beyond that? Do you really think the motion of pedals can't be described without using general relativity?