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An intuitive way to tell if something is a "real" force (as proposed to a pseudo- or fictitious force) - can someone subject to that force feel it, or equivalen
by antonvs 6y ago
An intuitive way to tell if something is a "real" force (as proposed to a pseudo- or fictitious force) - can someone subject to that force feel it, or equivalently, can an accelerometer measure the acceleration it produces?
When you accelerate or decelerate in a vehicle, you feel it. But when you jump out of a plane and accelerate towards the ground, you don't feel a force.
Noticing this fact was a big part of what led Einstein to his equivalence principle and General Relativity.
- basicplus2 6y agoWhat about when you splat on the ground? Is that not a force? Where did it come from?
- antonvs 6y agoThat involves a force which comes from encountering an object that's not in free fall with you.
- drivers99 6y agoSpecifically the electrons in the atoms of the ground and the electrons of the atoms of yourself repel each other when they come together. “So pushing just two atoms close to each other takes energy, as all their electrons need to go into unoccupied high-energy states. Trying to push all the table-atoms and finger-atoms together demands an awful lot of energy – more than your muscles can supply. You feel that, as resistance to your finger, which is why and how the table feels solid to your touch.“ https://theconversation.com/if-atoms-are-mostly-empty-space-why-do-objects-look-and-feel-solid-71742 https://theconversation.com/if-atoms-are-mostly-empty-space-...
- tim333 6y agoIn my high school we were taught the other way - that the gravity on you in free fall is a real force and centrifugal force going round a corner is not. It depends a bit how you define words like real.
- shawnz 6y agoIf all the particles in your body were made magnetic and you jump out of a plane on a weightless magnetic planet, how would it feel different than jumping out of a plane on Earth?