Question

F=ma. Therefore, is force a function of position or velocity?

Answer 1

Force is a function of none, and this is what i have been thinking, and my question that i have posted is because of this confusion

Answer 2

http://www.youtube.com/watch?v=h96SW0PfQcg 9 minutes in is similar to this, but I can't see why you can' just know the position to work out acceleration

Answer 3

I also don't get how knowledge of instantaneous position is enough to work out velocity.

Answer 4

well, if just define force in a general term then it is something that we push and pull, for example if we apply force on a wall, there is no displacement, no acceleration and no velocity which indicates force should be zero but there is force, newtons second law says rate of change of momentum is force but when we apply force on something that is stationary, there is force but net change in momentum is zero, therefore i am confused what exactly can we used to define force ?

Answer 5

http://openstudy.com/users/jemurray3#/updates/503d1afee4b04bebe0426c05

Answer 6

Carl Pham's answer posted here:

Force is something that causes an acceleration in a body that can move. It's directly experienced as a pressure or impulse. Why do we need a definition for a direct observation? That's like asking for a definition of length. Length is something we directly perceive, it needs no other definition than simply pointing to it.

Where we need definitions is of things that we cannot perceive directly, like inertial mass, or energy. These thins must be defined in terms of things we can observe, like forces and accelerations.

What you may be asking is what relationship force bears, mathematically, to the whole zoology of physics concepts. For example, force is a derivative of energy with respect to placement. But that's not a "definition" of force (if anything, it's a definition of energy), it's just the relationship between force and energy. That's because force comes first -- force is directly observable, energy is not.

This is not to say that you can't build up a coherent theory of physics starting from abstract principles and *deriving* the nature of force. That's certainly possible (at least, we hope so). But that still isn't really a definition of force, so much as stating where force fits in your abstract construction. Because science is fundamentally empirical: the proof of an abstract construction is its consistency with what's observable. That is, you may "derive" force if you like from abstract ideas (like energy), but your ideas must end up proving that force has the properties we know it has from direct observation. So the "derivation" can't possible come up with any new properties -- it's more like a proof than a derivation, perhaps, speaking mathematically.

Answer 7

most of the time i disagree and i condemn his line when he says " Why do we need a definition for a direct observation" i strictly disagree with this and i hope you are getting my logic that i just mentioned above

Answer 8

I think you're being too simplistic saying there is no displacement. There is a strain on the electromagnetic forces between the atoms in the wall, but the binding force increases its component horizontally as it is displaced very slightly horizontally in the other direction

Answer 9

To use a crude analogy: