Timeline for How does Newton's third law apply to an object interacting with air?
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| Oct 20, 2015 at 16:44 | comment | added | CR Drost | @PeterSchneider Yes, there is a way to refer to conservation of momentum as a force balance, but no, pedagogically we must treat them very differently, because students get very confused about the difference between "the force of gravity is balanced by the force of my chair on me" (which happens because I'm not accelerating -- what I've called a "force balance") and "the force of my chair on me is equal to the force of me on my chair" (Newton's third law). | |
| Oct 20, 2015 at 16:36 | comment | added | Peter - Reinstate Monica | Conservation of momentum and balance of forces are two faces of the same issue. Just because two interacting "entities" (say: solid bodies) experience the same (but opposite) forces for the same time (which is rather a truism) is it that the overall system "conserves momentum". That is true whether the body falls in earth's gravity field or whether it sits motionless in a chair so that all forces could be considered internal forces of the body earth. After all, nothing is really "touching" or "resting": everything interacts through dynamic field interactions. | |
| Oct 20, 2015 at 15:55 | history | answered | CR Drost | CC BY-SA 3.0 |