Force question

mvan4310

Hello,

I understand that force is mass x acceleration. What I don't understand is why acceleration and not velocity. Can someone explain why exactly

iceblits

well mass times velocity is actually something else..known as momentum
and force is actually the rate of change of momentum..you could perhaps try and read Newton's own writing on the matter to see how it was developed..I don't really know how to prove it :'(

mvan4310

Well that would explain it. My physics teacher never would explain why and he skipped momentum for some odd reason

iceblits

You should get to momentum afterwards I think

mvan4310

Ill dive into my college physics book when I have the chance. Thanks I appreciate the fast replies

AudioFlux

Suppose you are travelling in an elevator in gravity free space. If the elevator is moving with a constant velocity, you wouldn't even know that you are moving. But if it is accelerating, you would know, because you will be exerting a force on the floor of the elevator.

mvan4310

Well, I understand the acceleration aspect. Just wasnt sure why Force was mass by acceleration. Couldnt we say that an object traveling at a constant velocity that hits a motionless object imposes a force upon impact?

AudioFlux

Very true. That's because when the object moving with a constant velocity hits the motionless object, it decelerates and the motionless object accelerates from rest. Check this out: http://en.wikipedia.org/wiki/Impulse_(physics)

mvan4310

Wow, its the simple things I seem to not think of.... Lol

russ_watters

Er - I wouldn't say that. Impulse is not force. A collision does not have one single force associated with it, so it is far too simplistic to associate force with velocity.

Naty1

mvan: smart people have developed very exact definitions, such as force and momentum, acceleration and velocity, and refined them over many years...maybe even several thousand years. So no one should be surprised as they study that accumulated knowledge that it is not always obvious....especially at initial exposure.

Force is related to acceleration because a fixed unbalanced force acting on a mass causes a uniform acceleration, not a uniform velocity. A uniform velocity is associated with a fixed unbalanced force: zero.

One relationship between force and velocity: FT = MV

jetwaterluffy

If you send something at a velocity, it will stay at the same speed if not exerted on by a force.

Sammy8

This may be an off question, but what is Earth's movement classified as?

I'm guessing momentum: The sun being (mass x acceleration) creating the force (distance of mass). Then that force times the velocity of the mass to give our momentum.

Then you would basicly repeat this for the sun to the galaxy's center, and so on down to the center of space. Going from smallest body of mass to the largest.

Sammy8

I guess the suns force wouldnt be times velocity because it doesnt go at a uninterupted pace. The solar systems force/mass must be impacted by another force to create that momentum.

Maybe an insight to anti-matter? It wouldnt be pushed out and compressed or anything. Since the mass of the solar system is accelerating and spreading out It would actualy be bringing more of the anti-matter/space closer to its core. In other words a displacement of mass and space, the distance between mass.

So the velocity would be the suns force constant rate of speed, then times the force of the anti-matter/space to equal our momentum.

jetwaterluffy

The earth has an angular momentum whilst going around the sun, and the sun's force of gravity provides the Centripetal force.

Sefrez

Why not if a collision involves changing the sate of ones motion?

JHamm

If you like you can say it is a result of Newton's first law, that stuff which is already moving is going to just keep moving that way unless something makes it change, so a force causes a change in velocity rather than velocity itself, but I think it's fair to say that the reason something will just keep on moving the way it is without a force is at the moment unknown.