Question

what is force

Answer 1

something that causes acceleration (or deceleration)

Answer 2

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Answer 3

force is something which changes or tends to change the state of motion of a body

Answer 4

thank you krishnadas

Answer 5

but a force can hold something in place too

Answer 6

Nobody quite knows. This is one of the great mysteries. In classical, Newtonian, mechanics, force is just a magical influence that one body has on another, instantaneously, over distances small and enormous. Id est, the Sun just magically reaches out across 93 million miles and pulls at the Earth, in a way we can mathematically describe, and use to predict the relative motion of Sun and Earth.

Einstein put the spoke in the wheels of Newton by proving that nothing travels faster than the speed of light. He went on to explain gravity as not so much a force as a curving or wrinkling up of spacetime itself, which a massive body causes, and which can perturb the free motion of other massive bodies, just as the trajectory of a rolling ball may be perturbed from a straight line if the surface on which it rolls is curved. Indeed, if the surface is curved in just the right way, like a funnel, the free trajectory of a rolling ball will curve around in a closed elliptical orbit, just as if something at the center of the funnel were exerting some mysterious influence on it -- a classical Newtonian force.

This is well and good for gravity, but it doesn't work for other forces, specifically the electromagnetic force. There, we have to invoke a second sort of "spacetime," which is the electromagnetic field. This "background" on which charges move is curved and twisted by the presence of charges, and these curves and twists can interfere with the free trajectory of other charges in the vicinity. This is the basis of modern theories of electromagnetic -- and the other two forces, weak and strong nuclear force -- interactions. It gets around the problem of action at a distance, and instantaneous transmission of forces, because the body exerting a force just acts locally, to distort the field. This distortation then propagates outward at the speed of light, and then the affected body interacts again locally, just with the local field. No action at a distance, no instantaneous transmission of influences. It all works out.

Except, of course, we are left wondering about these fields. Why do these exist? How can they exist, separate from the bodies that cause them? They seem like a funny kind of deus ex machina, like the luminferous aether, introduced because we lack the imagination to see the simpler answer that is consistent with our experience, and the limitations imposed by the finite speed of light.

We don't know the resolution of these questions, so the true meaning of a force is something that remains for future generations to discover, if they can.

I am assuming, of course, that you understand just what a force feels like -- that you understand the practical definition of the word -- and that you are looking for a deeper explanation of what the phenomenon is.

Answer 7

force is a pull or push..