Understanding Force: Mass x Acceleration

In summary, force is defined as the rate of change of momentum, which is why it is expressed as mass multiplied by acceleration rather than velocity. This can be seen in collisions where a force is exerted to change the state of an object's motion. However, force is not the same as impulse, which is a measure of change in momentum over time and can involve multiple components and an average value.
  • #1
mvan4310
22
0
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
 
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  • #2
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 :'(
 
  • #3
Well that would explain it. My physics teacher never would explain why and he skipped momentum for some odd reason
 
  • #4
You should get to momentum afterwards I think
 
  • #5
Ill dive into my college physics book when I have the chance. Thanks I appreciate the fast replies
 
  • #6
Suppose you are traveling 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.
 
  • #7
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?
 
  • #8
mvan4310 said:
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?

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 [Broken])
 
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  • #9
AudioFlux said:
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 [Broken])

Wow, its the simple things I seem to not think of... Lol
 
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  • #10
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.
 
  • #11
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
 
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  • #12
If you send something at a velocity, it will stay at the same speed if not exerted on by a force.
 
  • #13
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.
 
  • #14
I guess the suns force wouldn't be times velocity because it doesn't 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 wouldn't 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.
 
  • #15
The Earth has an http://en.wikipedia.org/wiki/Angular_momentum" [Broken].
 
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  • #16
russ_watters said:
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.

Why not if a collision involves changing the sate of ones motion?
 
  • #17
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.
 
  • #18
Sefrez said:
Why not if a collision involves changing the state of ones motion?

Three reasons:
1) Impulse is not a force, it is a measure of change of momentum. Divide it by the time period it changes in, and you get the average net force.
2) Notice I said net force. The components of this force can be many different things.
3) Notice I said average force. In a collision, the net force often changes during the duration of the collision.
 
  • #19
jetwaterluffy said:
Three reasons:
1) Impulse is not a force, it is a measure of change of momentum. Divide it by the time period it changes in, and you get the average net force.
2) Notice I said net force. The components of this force can be many different things.
3) Notice I said average force. In a collision, the net force often changes during the duration of the collision.

I guess I am still speaking simplistically then. If impulse is the measure of change in momentum and you get the average change (some non-infinitesimal time interval), you get a average net force, correct? If so, I guess going back to a simplistic mode - ignoring what could be the components of the net force - it is, on that level of an ignorant mind - a force, right? Maybe a am being a little to philosophical? Nonetheless, I think I understand where russ was getting at now with it being simplistic from what you have said. :)
 
  • #20
Sefrez said:
I guess I am still speaking simplistically then. If impulse is the measure of change in momentum and you get the average change (some non-infinitesimal time interval), you get a average net force, correct? If so, I guess going back to a simplistic mode - ignoring what could be the components of the net force - it is, on that level of an ignorant mind - a force, right? Maybe a am being a little to philosophical? Nonetheless, I think I understand where russ was getting at now with it being simplistic from what you have said. :)
If you mean average change per unit time, then yes, you are right, if you are looking at it in a simplistic way. Remember, though, some materials will change the momentum faster than others, e.g. a metal ball will change the momentum faster than a pillow, so you will get different forces with the same impulse depending on the material.
 

What is force?

Force is a physical quantity that describes the interaction between objects. It can cause an object to accelerate, decelerate, or change direction.

How is force measured?

Force is measured in Newtons (N) using a spring scale or a force meter. One Newton is equal to the force required to accelerate 1 kilogram of mass at a rate of 1 meter per second squared (1N = 1kg x 1m/s²).

What is the relationship between force, mass, and acceleration?

The relationship between force, mass, and acceleration is described by the equation F=ma, where F is the force applied, m is the mass of the object, and a is the acceleration caused by the force. This means that the greater the mass of an object, the more force is needed to accelerate it.

How does an object's mass affect its acceleration?

An object's mass affects its acceleration inversely. This means that the greater the mass of an object, the smaller its acceleration will be when a force is applied. For example, a heavier object will require more force to accelerate at the same rate as a lighter object.

Can objects with the same mass have different accelerations?

Yes, objects with the same mass can have different accelerations if different amounts of force are applied to them. For example, a car and a bicycle may have the same mass, but the car would require more force to accelerate at the same rate as the bicycle due to its larger size and greater resistance to motion.

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