# Does momentum "get transferred" during collisions?

#### justme

Is it correct to talk about momentum being transferred between objects during collisions? Did classical physicists view it this way at all?
I have heard the expression before and as a physics educator I want to make sure I am using the right language.
By describing momentum this way it seems to be modelling momentum as a "thing" that can be transferred or flow around a system, like "energy" being transferred. And that fact that it is conserved during collisions makes this language even more tempting to me.
However I have also heard that is not right to think of it this way at all, it is far better to just restrict its description to being a mathematical quantity (mv).

#### oz93666

Well it is 'transferred' ... when a moving billiard ball hits another stationary one , some momentum passes over , is transferred ... this is a correct description of what is taking place ...

Mathematics has no place in describing what is happening , only in quantitative analysis ....IMHO

#### justme

ok...so if it is a "thing" that is transferred, what is a description of its properties? I can only describe it as mv...any other words or descriptions I find inaccurate eg an "indicator" of the ability to stop an object..but that description fits kinetic energy much better I feel.

#### studiot

Is it correct to talk about momentum being transferred between objects during collisions? Did classical physicists view it this way at all?
I have heard the expression before and as a physics educator I want to make sure I am using the right language.
By describing momentum this way it seems to be modelling momentum as a "thing" that can be transferred or flow around a system, like "energy" being transferred. And that fact that it is conserved during collisions makes this language even more tempting to me.
However I have also heard that is not right to think of it this way at all, it is far better to just restrict its description to being a mathematical quantity (mv).
I am very happy to discuss this, (and it leads to some deep Philosophy of Physics( but what sort of Physics are you a 'trainer' of, that you don't already have the answer?

Yes there was a time, before the word energy was invented, when one of the known types of energy was thought of as a substance, called caloric.
This view was later discredited.

Energy and momentum are properties of matter or substance, but they are not substances themselves.

But unlike mass, which is another property, you cannot 'transfer' a quantity of this property from one system to another.

Mass is a property that cannot be taken away from a body.

As to conservation laws it can be difficult to explain to beginners whether to use conservation of energy or conservation of momentum.
Iam am sorry to disillusion you, Oz, but you need Mathematics for this purpose.

Consider the following:

A rifle bullet of mass 0.1kg is fired at block of wood, of mass 1kg and situated on a long frictionless surface. The bullet impacts at 440m/s.
The impact embeds the bullet in the block and the two speed off at what velocity?

What is the kinetic energy before and after the impact?

1 person

#### justme

Thanks studiot
I am a high school physics teacher. My background is in engineering so my field is much more the application of physics rather than the understanding of the concepts. I feel I have an understanding of the concepts each in their own right, to the extent I can define them and use them to solve problems.
I would however like a better sense of knowledge of the subject to know the relationships between the fundamental concepts eg momentum mass energy time torque etc so they fit together into a coherent model in my mind, and for my students.
I realise at a higher academic level the universe can be thought of as a collection of separate abstract mathematical concepts rather than things, but that is not really the framework of high school physics.
I feel I need a deeper understanding of the classical physics model in the hope that it would be a system of defining physics in a way that was closer related to tangible concepts, and in a way that students can get their head around. Maybe with the idea of having a mind map of the physics concepts their relationship to each other.
I have seen the hyperphysics website and it is very close to what I am after but it doesnt show the momentum mass energy time torque etc on the same diagram so the relationships to me are still pretty fuzzy to me.

#### Pmb

PHF Hall of Fame
Is it correct to talk about momentum being transferred between objects during collisions? Did classical physicists view it this way at all?
I have heard the expression before and as a physics educator I want to make sure I am using the right language.
By describing momentum this way it seems to be modelling momentum as a "thing" that can be transferred or flow around a system, like "energy" being transferred. And that fact that it is conserved during collisions makes this language even more tempting to me.
However I have also heard that is not right to think of it this way at all, it is far better to just restrict its description to being a mathematical quantity (mv).

Yes. I can be transferred during collisions.

By the way. Energy is not a "thing." I.e. there's no such thing as energy.

For more on this please see: What is Energy?

Entire papers and books have been written on this subject. Think of energy in the same way an accountant think so money. Most of the money in the US is iomn computers recorded using 1's and 0's.

3 people

#### justme

Ok so there is no such thing as mass, energy or momentum..they are just "properties" of matter.
Can force be called a "property" of matter?
Can torque be called a "property" of matter?
Is matter a "thing"?

Thanks, I want to get the words right.

#### Pmb

PHF Hall of Fame
Ok so there is no such thing as mass, energy or momentum..they are just "properties" of matter.
Can force be called a "property" of matter?
Can torque be called a "property" of matter?
Is matter a "thing"?

Thanks, I want to get the words right.
What is a bookkeepers property of matter? I explained that's all energy is, bookkeeping. Did you read what's in the link I posted? I didn't post it for me help or to impress women or buy me more beer.

#### justme

What is a bookkeepers property of matter? I explained that's all energy is, bookkeeping. Did you read what's in the link I posted? I didn't post it for me help or to impress women or buy me more beer.
Thank you. I read your link and I can see that energy can be called a property of matter and treated in a bookkeeping way.

Now I have 3 other related questions:
1) Can force be called a "property" of matter? If not then what would you call it?
2)Can torque be called a "property" of matter? If not then what would you call it?
3) Is there such a thing as matter?

#### justme

If energy does not exist and is a bookkeeping concept...why is it accurate for a physicist to describe energy as being absorbed?

....thats what my Oxford textbook on IB physics does.