Quote:
Erick Mead wrote:
...If you are a static intermediate structure between two objects pushing at one another (Newton's Third Law I believe) through your structure, your structure is necessarily and unavoidably exerting equal and opposite force against BOTH of them. If you are a eighty-year old man and you become the intermediary for the hammer and the planet, then you likely break something along the way.
Your structure is pushing back in each case. If not, then you are being moved somewhere, because you are not resisting. Basically, those are the two choices in repsonse to applied force, either resist or accelerate.
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I think the best way to describe the structure is "sprung"...rather than "rigid". Obviously there are varying degrees of "springiness" and "rigidity"... But it has to do with conservation of linear momentum and elastic (or in varying cases... partially elastic) collisions - a combination of Newton's 1st and 3rd laws...
It's like that suspended ball bearing contraption, whereby if the ball on one end is swung and hits the other balls, the balls in the middle remain stationary, and kinetic energy is transferred to the opposite end ball and so on. Obviously there will be some loss of KE, and conversion to PE, but the total momentum and energy within that isolated system is conserved. I think...
If the opposite end ball is somehow prevented from swinging, perhaps by being in contact with a wall, then KE is transferred to the wall. And because the wall (ground?) is THE rigid structure, Newton's 3rd law applies, and the KE is transferred back to the first ball, causing it to swing back (i.e. the 1st law).
So, your structure is not "pushing" back... or rigid, but sprung. You're just the balls in the middle. And you are merely attempting to manipulate the kinetic energy, thru your structure, against the ground and back, so that the total momentum is more or less conserved, thus restoring "harmony".
Well, at least how I understand it... my physics sux, so I could be way off the mark...in terms of the physics...
