What is the difference between momentum and kinetic energy?

[aloshi]

Hello!
yes is from Sweden and my English is not good, but will try to do as best as possible. My question is:
why can not consider the momentum as the acceleration energy?

I know that:
Impulse is change in momentum which is not the same as energy
Impulse can be expressed either as F * (delta) t or m * (delta) v since it is the same thing. That the expressions are as follows from Newton's 2nd Kraftlag together with the definition of acceleration: (delta) v / (delta) t

but as we move into the energy we see that energy is defined as:
W = mv ^ 2 / 2

if we compare the energy between, thus förendringen Middle two speeds we get that the change in energy is:
http://www.pluggakuten.se/wiki/image...itled11111.jpg
I can not see a big difference between them, the only thing that separates them is that we have abbreviated removed (delta)stretch

but what is the difference between rörelsenergi and momentum:

I couple of things:
An important difference is that momentum is always kept in a collision between two or more objects. The kinetic energy conservation is generally not in a collision.
Another difference between kinetic energy and momentum is that kinetic energy is a scalar (ie, has size but not direction) while the momentum is a vector (ie, both the size and direction)

but I can not really understand what the difference between momentum and kinetic energy (accelerating energy)

 

[aloshi]

Hello!
yes is from Sweden and my English is not good, but will try to do as best as possible. My question is:
why can not consider the momentum as the acceleration energy?

I know that:
Impulse is change in momentum which is not the same as energy
Impulse can be expressed either as $$F \cdot \Delta t$$ or m * (delta) v since it is the same thing. That the expressions are as follows from Newton's 2nd Kraftlag together with the definition of acceleration: (delta) v / (delta) t

but as we move into the energy we see that energy is defined as:
W = mv ^ 2 / 2 $$mv ^ 2 / 2$$

if we compare the energy between, thus förendringen Middle two speeds we get that the change in energy is:
http://www.pluggakuten.se/wiki/image...itled11111.jpg
I can not see a big difference between them, the only thing that separates them is that we have abbreviated removed (delta)stretch

but what is the difference between rörelsenergi and momentum:

I couple of things:
An important difference is that momentum is always kept in a collision between two or more objects. The kinetic energy conservation is generally not in a collision.
Another difference between kinetic energy and momentum is that kinetic energy is a scalar (ie, has size but not direction) while the momentum is a vector (ie, both the size and direction)

but I can not really understand what the difference between momentum and kinetic energy (accelerating energy)

 

[aloshi]

Hello!
yes is from Sweden and my English is not good, but will try to do as best as possible. My question is:
why can not consider the momentum as the acceleration energy?

I know that:
Impulse is change in momentum which is not the same as energy
Impulse can be expressed either as F * (delta) t or m * (delta) v since it is the same thing. That the expressions are as follows from Newton's 2nd Kraftlag together with the definition of acceleration: (delta) v / (delta) t

but as we move into the energy we see that energy is defined as:
W = mv ^ 2 / 2

if we compare the energy between, thus förendringen Middle two speeds we get that the change in energy is:
http://www.pluggakuten.se/wiki/image...itled11111.jpg
I can not see a big difference between them, the only thing that separates them is that we have abbreviated removed (delta)stretch

but what is the difference between rörelsenergi and momentum:

I couple of things:
An important difference is that momentum is always kept in a collision between two or more objects. The kinetic energy conservation is generally not in a collision.
Another difference between kinetic energy and momentum is that kinetic energy is a scalar (ie, has size but not direction) while the momentum is a vector (ie, both the size and direction)

but I can not really understand what the difference between momentum and kinetic energy (accelerating energy)[/QUOTE]

Hello!
yes is from Sweden and my English is not good, but will try to do as best as possible. My question is:
why can not consider the momentum as the acceleration energy?

I know that:
Impulse is change in momentum which is not the same as energy
Impulse can be expressed either as $$F \cdot \Delta t$$ or $$m \cdot \Delta v$$ since it is the same thing. That the expressions are as follows from Newton's 2nd Kraftlag together with the definition of acceleration: (delta) v / (delta) t

but as we move into the energy we see that energy is defined as:
$$mv ^ 2 / 2$$

if we compare the energy between, thus förendringen Middle two speeds we get that the change in energy is:
http://www.pluggakuten.se/wiki/image...itled11111.jpg
I can not see a big difference between them, the only thing that separates them is that we have abbreviated removed (delta)stretch

but what is the difference between rörelsenergi and momentum:

I couple of things:
An important difference is that momentum is always kept in a collision between two or more objects. The kinetic energy conservation is generally not in a collision.
Another difference between kinetic energy and momentum is that kinetic energy is a scalar (ie, has size but not direction) while the momentum is a vector (ie, both the size and direction)

but I can not really understand what the difference between momentum and kinetic energy (accelerating energy)

 

[tiny-tim]

Welcome to PF!

Hello! Hello! Hello! Welcome to PF!

I'm not sure what you mean by "acceleration energy" or "rörelsenergi", and your link isn't working, but anyway …

From the chain rule, d(mv)/dt = d(mv)/ds ds/dt = d(mv)/ds v = d(1/2 mv²)/ds.

Does that help?

 

[aloshi]

In order to acceleration, there must be a job. that is what I call the acceleration energy thus acceleration work. acceleration of work is $$F\cdot \Delta s$$ and this means increasing the kinetic energy. therefore increases speed.

what would be linked are:
http://img195.imageshack.us/img195/4176/40958030.jpg



what I can not understand the difference between kinetic energy and momentum is not so great. we have only shortened away $$\Delta s$$[/QUOTE]

 

[aloshi]

This link shows how I have been derived momentum and nothing else-:
http://img195.imageshack.us/img195/4176/40958030.jpg

 

[tiny-tim]

Hi aloshi!

(have a delta: ∆ and try using the X² tag just above the Reply box )

Yes, I can see your link now.

I'll rewrite it so that it's easier to read …

If we have a very small increase in speed, from v to v + ∆v,

then ∆KE = 1/2 m ((v + ∆v)² - v²) = mv ∆v = m ∆s/∆t ∆v = m ∆s (m∆v/∆t) = ∆s F,

which is the standard work-energy theorem, change in KE = work done by force F moving through distance s.

(I've used Newton's second law : impulse = force x time = change of momentum, or F ∆t = ∆(mv))​

After that, I don't follow what your objection is.

Are you confusing impulse with work done ?

Impulse = force x time, but work done = force x distance.

Are you saying that for a very small change, distance is proportional to time, and so impulse is proportional to work done? If so, that ignores the fact that, if there is acceleration, distance is never proportional to time (except in circular motion, in which case the work done and the change in KE are zero).

 

[aloshi]

i can't understand what is the difference between Newton's second law and the momentum?

 

[tiny-tim]

i can't understand what is the difference between Newton's second law and the momentum?

Newton's second law : impulse = force x time = change in momentum

(or force = rate of change of momentum).

What is worrying you about that?

 

[aloshi]

I can not understand the properties of momentum has. what is momentum?

 

[tiny-tim]

I can not understand the properties of momentum has. what is momentum?

Momentum is mass times velocity.

It is the derivative of kinetic energy … mv = d/dt (1/2 mv²)

 

[aloshi]

what is the difference physically, I understand the difference mathematical

 

[tiny-tim]

momentum equals available "oomph"

Momentum is always conserved in collisions (while kinetic energy is not),

so momentum measures the "oomph" available when something hits something else.

 

[aloshi]

I could not be pushed to the last:

"So the momentum measures the" oomph "available when something hits something else"
can you explain thanks

 

[tiny-tim]

Momentum is a quantity which an object has when it moves.

It can transfer that quantity to another object.

That quantity is never lost, it only moves from one object to another.

It measures the ability to move another object …

the more momentum you have, the more you can move something else …

the less you have, the less you can move something else …

if you do move something else, you must give up some of your own momentum.

 

[aloshi]

Requires no energy to give over part of their own speed?

 

[tiny-tim]

Requires no energy to give over part of their own speed?

Change of energy is not required …

if you bounce a ball off a wall, there is no change of energy, but the ball exerts an impulse on the wall …

if the wall is on wheels, it will move, with little or no change in the energy of the ball.

What moves the wall is the change in momentum: the change in energy is irrelevant.

 

[aloshi]

if we are dragging a ball from a height H. After the nozzles have the floor, it will not reach to the height H, but it will not be as high. it mean that we have lost energy?

if we are dragging a ball from a height H. After the nozzles have the floor, it will not reach to the height H, but it will not be as high. it does not mean that we have lost energy?
it can not mean that the floor gave a speed, and therefore its momentum. floor can not get a speed

 

[tiny-tim]

if we are dragging a ball from a height H. After the nozzles have the floor, it will not reach to the height H, but it will not be as high. it does not mean that we have lost energy?

Yes, if we drop a ball from a height H (sorry, i have no idea what you mean by "nozzles" ), it will not quite return to height H because of the small amount of thermal energy (heat) generated.

But that energy creates heat (and/or vibration and noise), not movement.

it can not mean that the floor gave a speed, and therefore its momentum. floor can not get a speed

No, the floor does get a speed …

the floor is fixed to the Earth, and when the ball bounces up, the whole Earth moves very very very slightly down!

 

[aloshi]

there are other ways of thinking that momentum? I want to understand it to 100%

 

[tiny-tim]

there are other ways of thinking that momentum? I want to understand it to 100%

No, I think I've covered everything, but if you still have any questions, just ask.

 

[aloshi]

No, I think I've covered everything, but if you still have any questions, just ask.

I do not know how to thank you, you have taught me much that my teachers could not teach me. I have that project and have chosen to investigate Compton scattering / Compton effect. Then I read about it, I saw that the momentum is the key element. so I've probably other issues that I need to ask. but it will be later, please respond during the Christmas holidays?

I will read more about momentum, therefore, I wondered if there was anything more that you can mention. thanks

 

[tiny-tim]

I assume you're starting with http://en.wikipedia.org/wiki/Compton_scattering" ?

Remember that both momentum and energy are conserved in Compton scattering.

(In a collision, to solve the equations, you need both conservation of momentum and either conservation of energy or some physical constraint such as a fixed speed.)

On momentum itself, you might also like to read the PF Library article at https://www.physicsforums.com/library.php?do=view_item&itemid=183", and the Australian website referred to in it, about how conservation of momentum explains how a sound wave can be reflected from the open end of a pipe.

happy holidays!​

 

[aloshi]

Can there is more fuller on Compton scattered? Then other links

 

[tiny-tim]

google book search

Can there is more fuller on Compton scattered? Then other links

Try a google book search …

on the google search page, type "Compton scattering" (including the quotation marks), then click on the drop-down menu marked "more" at the top of the page, and click on the first item, which is "Books" …

that will give you a lot of books on Compton scattering (for example, http://books.google.com/books?id=u7...r&dq="Compton+scattering"&client=safari&cd=1"), and any that are marked "Limited preview" can be read and downloaded free.

 

[aloshi]

Momentum is a quantity which an object has when it moves.

It can transfer that quantity to another object.

That quantity is never lost, it only moves from one object to another.

It measures the ability to move another object …

the more momentum you have, the more you can move something else …

the less you have, the less you can move something else …

if you do move something else, you must give up some of your own momentum.

you say that each okjekt has one quantity, then is my question: What comes this from the start? if we say a car, in order to it will drive so needs it no quantity from another item without it needs fuel in order to begin to drive. therefore, that one energy needs in order to can to drive with the car. if we take another example and it is then one runs. before I began to run had I no momentum, without in order to I will can opening so needs I to allocate a certain energy. this energy comes from the food that I eat. about now I run and since collides with another item that is placid comes a part of my momentum to be transferred to the item, but was come my momentum from? it cannot well come how as entire pcs, without it must come from something. I do not know about my English is understand

 

[tiny-tim]

Hi aloshi! Happy new year!

ok, you're asking where does the momentum come from, for example when a car accelerates, or when a person runs?

For a car, the extra momentum comes from the momentum of the piston, which in turn comes from the momentum of the gas molecules hitting the piston, which in turn comes from a chemical reaction …

the chemical reaction is basically the breaking of a bond … two objects are bound together with potential energy of a force field, and when that potential energy is released, the two objects fly apart.

Consider dropping something from a height … it will hit the ground with great momentum, but where did that momentum come from?

It also came from the potential energy of a force field (in this case, a gravitational field, but in the case of a chemical bond, it would be an electromagnetic field).

Basically, when a car accelerates, or when a person runs, ultimately the momentum has come, not from a collision, but from the release of energy of a force field

hmm … the Moon's momentum now is completely opposite to what it was two weeks ago … where did that change of momentum come from (since the potential energy is roughly the same)?

dunno! … i'll have to let someone else try to explain that ​

 

[aloshi]

thanks for the reply, but can you explain dett here once more:
the chemical reaction ice basically the breaking of a bond… two objects are bound together with potential energy of a force field, wild duck when that potential energy ice released, the two objects escape apart.

hag is not good on English and I translate the text in google translates. but it is value loose

 

[tiny-tim]

I always think of breaking a chemical bond as being like cutting an elastic band … the stored energy is released, and the two sides fly apart.

I really don't know enough chemistry to explain it any better.

 

[aloshi]

have you a good homepages where it stand about business amount? would you kuna send little lhemsidor (web) to me thanks

 

[tiny-tim]

hag is not good on English and I translate the text in google translates. but it is value loose

have you a good homepages where it stand about business amount? would you kuna send little lhemsidor (web) to me thanks

your google translator is really bad!

i can usually guess what you mean, but this time i have no idea.

 

[aloshi]

I wondered about there be websites that explain momentum

 

[tiny-tim]

Try this free online book … http://books.google.com/books?id=bY...ontcover&dq=momentum&lr=&client=safari&cd=31" by David P. Kessler, Robert Albert Greenkorn

Also The forces of nature by P. C. W. Davies.

(btw, your English is much better than the google translator … i recommend that you do your own translation! )

 

[aloshi]

Try this free online book … http://books.google.com/books?id=bY...ontcover&dq=momentum&lr=&client=safari&cd=31" by David P. Kessler, Robert Albert Greenkorn

Also The forces of nature by P. C. W. Davies.

(btw, your English is much better than the google translator … i recommend that you do your own translation! )

have you easier level, I mean that my level is not so here advanced

 

[tiny-tim]

You could try Chapter 11 of http://books.google.com/books?id=Wk...ient=safari&cd=62#v=onepage&q=impact&f=false" by Sander Bais (2005)