# Impulse is change in momentum

#### tiny-tim

Homework Helper
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

Re: momentum

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

Homework Helper
I assume you're starting with http://en.wikipedia.org/wiki/Compton_scattering" [Broken]?

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!​

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#### aloshi

Re: momentum

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

#### tiny-tim

Homework Helper

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=u7jIIpZrECAC&printsec=frontcover&dq="Compton+scattering"&client=safari&cd=1"), and any that are marked "Limited preview" can be read and downloaded free.

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#### aloshi

Re: momentum

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 transfered 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

Homework Helper
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

Re: momentum

thanks for the reply, but can you explain dett here once more:
the chemical reaction ice basically the breaking of a bondâ€¦ 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

Homework Helper
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

Re: momentum

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

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#### tiny-tim

Homework Helper
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

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

#### aloshi

Re: momentum

I wondered about there be websites that explain momentum

#### tiny-tim

Homework Helper
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#### aloshi

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#### aloshi

Re: momentum

I have read "An elementary treatise on mechanics" and i have some difficulty in understanding.

1)
“When two bodies in motion impinge, if their centers of inertia move in the same straight line perpendicular to a plane tangent to the bodies at their point of contact , the impact is said to be direct and central.”
I can not really understand:
“the same straight line perpendicular to a plane tangent to the bodies at their point of contact”
if I'm drawing a picture of how the impinge look;
[PLAIN]http://www.pluggakuten.se/wiki/images/2/22/F%C3%B6rsta.jpg [Broken] [Broken]

[PLAIN]http://www.pluggakuten.se/wiki/images/2/22/F%C3%B6rsta.jpg [Broken] [Broken]

Have I understand’t correct?

2)
I can not really understand:
“if the straight line described by the center of inertia of one of the bodies is not perpendicular to the tangent plane , the impact is said to be oblique.”

if I'm drawing a picture of how the impinge look:

[PLAIN]http://www.pluggakuten.se/wiki/images/c/c7/Andra.jpg [Broken] [Broken]

[PLAIN]http://www.pluggakuten.se/wiki/images/c/c7/Andra.jpg [Broken] [Broken]
Have I understand’t correct?

it is from 240. DEF. in "An elementary treatise on mechanics"

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#### tiny-tim

Homework Helper
1)
“When two bodies in motion impinge, if their centers of inertia move in the same straight line perpendicular to a plane tangent to the bodies at their point of contact , the impact is said to be direct and central.”
I can not really understand:
“the same straight line perpendicular to a plane tangent to the bodies at their point of contact”

2)
I can not really understand:
“if the straight line described by the center of inertia of one of the bodies is not perpendicular to the tangent plane , the impact is said to be oblique.”
Hi aloshi!

The "tangent plane" is the plane of contact between the two spheres …

imagine that, when they are touching, you put a flat piece of paper between them …

it will be tangent to both spheres at the point of contact.

Now, it's possible for one (or both) of the spheres to come towards that paper at an angle (though still hitting the same contact point) …

in that case, the centre of inertia is not moving perpendicular to the tangent plane.

#### aloshi

Re: momentum

Hi aloshi!

The "tangent plane" is the plane of contact between the two spheres …

imagine that, when they are touching, you put a flat piece of paper between them …

it will be tangent to both spheres at the point of contact.
http://www.pluggakuten.se/wiki/images/8/83/Papper.jpg [Broken]

Now, it's possible for one (or both) of the spheres to come towards that paper at an angle (though still hitting the same contact point) …

in that case, the centre of inertia is not moving perpendicular to the tangent plane.
http://www.pluggakuten.se/wiki/images/0/0e/Snett.jpg [Broken]

like that??

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#### tiny-tim

Homework Helper
like that??
That's it! :tongue2:

Sphere B is approaching obliquely, and the impact is oblique.

#### aloshi

Re: momentum

can you help me with this too, thanks;

"When the bodies impinge, they exert a mutual but varying pressure during the interval between contact and separation, an interval of time which is generally very short, and we suppose them to suffer a degree of compression, by wich, during a portion of this interval, their centers will approach each other, and during the remaining portion will recede by the action of an internal force rending to restore them to their original form. The force urging the approach if their centers is called the force of compression; the opposing force causing them to separate again is called the force of restitution or elasticity. The ratio of the force of restitution to that of compression is called the modulus of elastisk"

1)what is/does meant by compression?
the force that the balls come into each other, collide(the force at collide)??

2)what is/does meant by restitution? the force that removes them?
3)what is/does meant by “The ratio of the force of restitution to that of compression is called the modulus of elastisk” ?

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"Impulse is change in momentum"

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