4 ms·
It's hard to better than Don Koks on this point <https://math.ucr.edu/home/baez/physics/General/Weight/whatIsWeight.html https://math.ucr.edu/home/baez/physics/
by raattgift 4y ago
It's hard to better than Don Koks on this point <https://math.ucr.edu/home/baez/physics/General/Weight/whatIsWeight.html https://math.ucr.edu/home/baez/physics/General/Weight/whatIs...> ("What is weight?", Usenet Physics FAQ, 2014).
The contact camp agrees with you.
I'm in the contact camp: a scale or balance blocks the freely falling motion of the weighed item. Or, by equivalence, the weighing apparatus (and anything supporting it, be it the whole planet Earth or a rocket engine) imparts an acceleration (i.e., applies a force) on the weighed item, so the latter cannot be in geodesic motion.
- kazinator 4y agoThe free-body diagram of the object has to show two balanced forces: the scale pushing on it, and gravity pulling on it. The net force is zero. When forces balance, they may balance to zero so the object in question doesn't move; but there is compression or tension in it. The scale measures that stress. If you remove either gravity or the restraining support (floor, table, ...) the stress goes away. Force is defined as mass times acceleration: F = ma. A body falling due to gravity experiences a force because it has mass and is accelerating. That's how force is defined.
- jenadine 4y agoThere are some "real" physical force that do not depend on the reference frame and are caused by some law of nature. And there are pseudo-forces that are just a mathematical artifact of a non inertial référence frame. Gravity is a pseudo force. https://en.wikipedia.org/wiki/Fictitious_force https://en.wikipedia.org/wiki/Fictitious_force
- kazinator 4y agoNon-intertial-reference forces can be traced to real forces if we change the reference frame. In an accelerating car, the seat really is pushing on your back. This is readily evident from the stationary reference frame. You're being accelerated and so there is a F = ma there. Centrifugal force is pseudo, but centripetal acceleration isn't. In what reference frame can we properly understand gravitational attraction, if the obvious one is fictional?
- jenadine 3y agoThe seat is pushing me in the car and the earth is pushing my feet when I stand up on it. The frame of reference is the curved 4 dimensions space-time https://en.m.wikipedia.org/wiki/Minkowski_space https://en.m.wikipedia.org/wiki/Minkowski_space
- deleted 3y ago[deleted]