Apologies, there are a couple of number typos in the first one.
Here is the corrected version:
Velocity is the speed and direction at which an object moves.
Force is something with a strength and a direction that causes
acceleration on the object and has an effect on its velocity.
Think about it like this:
You have some object, that is flying through space with a VELOCITY.
Maybe it is flying upwards, so the DIRECTION it is flying in would be
[0, 1, 0].
And let's say that it is flying with a SPEED of 6 units per second.
Those are the two components our velocity is made of: In what
direction is it flying and how fast is it flying there?
In ICE these two values are one vector [0, 6, 0] which you get by
multiplying the SPEED (6) with the DIRECTION ([0, 1, 0]).
When you multiply a vector(a row of numbers) with a scalar(a single
number) you simply multiply each element of the vector with the scalar.
[6*0, 6*1, 6*0] = [0, 6, 0] = the VELOCITY of the object
Now there is also the FORCE and this could be for example gravity or a
wind blowing, just anything that will move the object.
What properties does a force have?
It pushes things in a certain DIRECTION.
It pushes things with a certain STRENGTH.
Let's say our force pushes to the left, so in Softimage it's DIRECTION
would be [1, 0, 0].
And let's say that the STRENGTH of the forces push is 8.
Once again these two properties of the force are represented in one
vector [8, 0, 0] which you get by multiplying the STRENGTH(8) with the
DIRECTION ([1, 0, 0]).
[8*1, 8*0, 8*0] = [8, 0, 0] = the FORCE.
So now that we have a good idea of what a force and a velocity are
let's see what happens when the force acts upon our little object.
The object is moving through space with the VELOCITY [0, 6, 0] and
suddenly there is the FORCE [8, 0, 0] acting on it. Maybe an
interstellar wind started blowing...
The FORCE is acting on the object and wants to push it in another
direction/speed, which would give it a new VELOCITY since velocity =
speed*direction.
But the object also has MASS, that is a measure of how resistant to
changing velocity an object is. Let's say it has the MASS 4.
Now the force is still going to change the velocity of the object, but
the effect will be reduced by the mass.
The formula for how it is going to be reduced by the mass, comes from
the famous formula F=m*a ( force = mass * acceleration )
If we divide both sides of that equation by mass we get:
F/m = a ( force / mass = acceleration)
This tells us that we must divide our FORCE (F) by the MASS (m) to get
the acceleration.
Force: [8, 0, 0]
Mass: 4
[8, 0, 0] / 4 = [8/4, 0/4, 0/4 = [2, 0, 0] = acceleration
Now all you have to do once you have computed your acceleration is to
add it your velocity, to see what new velocity the force pushed it in.
So: PreForceVelocity + acceleration = PostForceVelocity
Velocity = [0, 6, 0]
Acceleration = [2, 0, 0]
[0, 6, 0] + [2, 0, 0] = [0+2, 6+0, 0+0] = [2, 6, 0] = PostForceVelocity
After our Object travelling with a mass of 4 and a velocity of [0, 6,
0] interacted with a force of [8, 0, 0] its new velocity is [2, 6, 0]
A bit elaborate, but I hope it helps you gain some intuition.
On Wed, Feb 13, 2013 at 12:24 PM, Leonard Koch
<leonardkoch...@gmail.com <mailto:leonardkoch...@gmail.com>> wrote:
Velocity is the speed and direction at which an object moves.
Force is something with a strength and a direction that causes
acceleration on the object and has an effect on its velocity.
Think about it like this:
You have some object, that is flying through space with a VELOCITY.
Maybe it is flying upwards, so the DIRECTION it is flying in would
be [0, 1, 0].
And let's say that it is flying with a SPEED of 6 units per second.
Those are the two components our velocity is made of: In what
direction is it flying and how fast is it flying there?
In ICE these two values are one vector [0, 6, 0] which you get by
multiplying the SPEED (5) with the DIRECTION ([0, 1, 0]).
When you multiply a vector(a row of numbers) with a scalar(a
single number) you simply multiply each element of the vector with
the scalar.
[6*0, 6*1, 6*0] = [0, 6, 0] = the VELOCITY of the object
Now there is also the FORCE and this could be for example gravity
or a wind blowing, just anything that will move the object.
What properties does a force have?
It pushes things in a certain DIRECTION.
It pushes things with a certain STRENGTH.
Let's say our force pushes to the left, so in Softimage it's
DIRECTION would be [1, 0, 0].
And let's say that the STRENGTH of the forces push is 8.
Once again these two properties of the force are represented in
one vector [2, 0, 0] which you get by multiplying the STRENGTH(8)
with the DIRECTION ([1, 0, 0]).
[8*1, 8*0, 8*0] = [8, 0, 0] = the FORCE.
So now that we have a good idea of what a force and a velocity are
let's see what happens when the force acts upon our little object.
The object is moving through space with the VELOCITY [0, 6, 0] and
suddenly there is the FORCE [8, 0, 0] acting on it. Maybe an
interstellar wind started blowing...
The FORCE is acting on the object and wants to push it in another
direction/speed, which would give it a new VELOCITY since velocity
= speed*direction.
But the object also has MASS, that is a measure of how resistant
to changing velocity an object is. Let's say it has the MASS 4.
Now the force is still going to change the velocity of the object,
but the effect will be reduced by the mass.
The formula for how it is going to be reduced by the mass, comes
from the famous formula F=m*a ( force = mass * acceleration )
If we divide both sides of that equation by mass we get:
F/m = a ( force / mass = acceleration)
This tells us that we must divide our FORCE (F) by the MASS (m) to
get the acceleration.
Force: [8, 0, 0]
Mass: 4
[8, 0, 0] / 4 = [8/4, 0/4, 0/4 = [2, 0, 0] = acceleration
Now all you have to do once you have computed your acceleration is
to add it your velocity, to see what new velocity the force pushed
it in.
So: PreForceVelocity + acceleration = PostForceVelocity
Velocity = [0, 6, 0]
Acceleration = [2, 0, 0]
[0, 6, 0] + [2, 0, 0] = [0+2, 6+0, 0+0] = [2, 6, 0] =
PostForceVelocity
After our Object travelling with a mass of 4 and a velocity of [0,
6, 0] interacted with a force of [8, 0, 0] its new velocity is [2,
6, 0]
A bit elaborate, but I hope it helps you gain some intuition.
On Wed, Feb 13, 2013 at 12:16 PM, Raffaele Fragapane
<raffsxsil...@googlemail.com <mailto:raffsxsil...@googlemail.com>>
wrote:
Reading that after sending it (when else would one proof
read?) I realize it might come across as a bit aggressive with
the opening comment.
My apologies to César if that's the case, it sure wasn't
intended to be or to discourage someone else away from
contributing to the already rare physics discussions.
Oliver, Wikipedia has excellent resources about these
subjects, just look up Newtonian physics and wiki hop around
to the specific words you wanted the meaning of.
On Feb 13, 2013 10:08 PM, "Raffaele Fragapane"
<raffsxsil...@googlemail.com
<mailto:raffsxsil...@googlemail.com>> wrote:
It's actually incorrect more so than clear.
Distance traveled divided by time is not velocity. It's
speed, a scalar value.
Velocity has to do with the rate of change and is
represented by a vector providing direction, and it's
magnitude representing speed. So while speed is the simple
speed an object travels at, velocity also specifies direction.
A force is represented similarly to velocity and
has/affects (depending on the approach, generally correct
if considered affecting) mass, it's effect results in the
affected body's velocity. A force is basically something
affecting another entity into change. It can be summarized
in push or pull efforts.
Acceleration is the rate of change of speed.
This is for Newtonian physics, or vectorial physics, the
most common kind in CG related models.
On Feb 13, 2013 9:52 PM, "olivier jeannel"
<olivier.jean...@noos.fr <mailto:olivier.jean...@noos.fr>>
wrote:
Thank's César ! Now it's clear :)
Le 13/02/2013 11:13, César Sáez a écrit :
They are completely different concepts, in short:
Force = mass * acceleration
Acceleration = Velocity / time
Velocity = distance-traveled / time
