Angular Momentum

[Count Igor]

First of all, I hope this is the right forum.
Anyway, I'm doing a very small presentation on Black Holes. Only a part of it, as I'm a thick brick.

But I've been having trouble with the idea of Angular Momentum while working out the electric charge, etc.
I will be back with more problems if I have them.
What I'm looking for is Angular Momentum for dummies. As I only have a very rough idea of what it is.

In fact, any information on Black Holes would be welcome.
I come to you, as I know you're all just so damn clever and we have a few physicists here.
(Sorry for being thick)

 

[SckizoBoy]

I don't think angular momentum and electric charge can really be associated with each other...

Anyway, best way I can think of explaining it as follows:

Analogy - you have a ball on the end of the string, and you're holding the other end. Now, twirl it around above your head so it's basically describing a circle.

What you have there is something (i.e. the ball) whose linear momentum (movement direction/speed in cartesian coordinates i.e. velocity) is constantly changing, because it goes from behind, accelerates fowards before slowing down and accelerating back again. However, it's angular momentum (movement direction/speed with respect to its axis of momentum) never changes (effectively) because the hand that holds the other end of the string isn't moving either.

Thus, angular momentum is the movement of an object (typically a satellite, context based label) with respect to a fixed point in space (i.e. change in distance from said point and speed (not velocity) with which it moves).

Not the best explanation, see if cookyy2k's about, he's a physicist, as I am but a mere chemist! *hrk*

 

[Count Igor]

I don't think angular momentum and electric charge can really be associated with each other...

Anyway, best way I can think of explaining it as follows:

Analogy - you have a ball on the end of the string, and you're holding the other end. Now, twirl it around above your head so it's basically describing a circle.

What you have there is something (i.e. the ball) whose linear momentum (movement direction/speed in cartesian coordinates i.e. velocity) is constantly changing, because it goes from behind, accelerates fowards before slowing down and accelerating back again. However, it's angular momentum (movement direction/speed with respect to its axis of momentum) never changes (effectively) because the hand that holds the other end of the string isn't moving either.

Thus, angular momentum is the movement of an object (typically a satellite, context based label) with respect to a fixed point in space (i.e. change in distance from said point and speed (not velocity) with which it moves).

Not the best explanation, see if cookyy2k's about, he's a physicist, as I am but a mere chemist! *hrk*

That does help, thanks very much.
But they're associated (As far as I know with my limited knowledge) when working them out using the Mass. I won't go into details, but I didn't mean anything further than that. [smiley face]

 

[Jordi]

I don't think angular momentum and electric charge can really be associated with each other...

Isn't angular momentum the thing that prevents electrons from collapsing into the (positively charged) core of the molecule they're orbiting? I'm just trying to remember things from high school here, so I'm probably wrong though.

 

[Redingold]

Well, angular momentum is equal to the mass of the object multiplied by its speed multiplied the distance between the object and the point it is orbiting. In quantum mechanics, it is quantized in multiples of h/2pi, I think, though I'm no expert.

 

[SckizoBoy]

Isn't angular momentum the thing that prevents electrons from collapsing into the (positively charged) core of the molecule they're orbiting? I'm just trying to remember things from high school here, so I'm probably wrong though.

I don't think so, it's merely the property of its movement. Anyway, quantum mechanics (or some such train of thought *mock-pretentious snif*) shows that traditional circular/spherical orbit isn't actually the case for subatomic particles.

Then again, I'm probably wrong. =P

Where's a physicist when you need one?! *hrk*

What's strange, though, is that somehow, they've found that electrons are the epitome of perfect spheres... apparently...

 

[Blue_vision]

Well, angular momentum is equal to the mass of the object multiplied by its speed multiplied the distance between the object and the point it is orbiting. In quantum mechanics, it is quantized in multiples of h/2pi, I think, though I'm no expert.

Yep.

OP, are you looking for Angular Momentum in terms of Quantum Physics, like spin?

 

[CrystalShadow]

Isn't angular momentum the thing that prevents electrons from collapsing into the (positively charged) core of the molecule they're orbiting? I'm just trying to remember things from high school here, so I'm probably wrong though.

I don't think so, it's merely the property of its movement. Anyway, quantum mechanics (or some such train of thought *mock-pretentious snif*) shows that traditional circular/spherical orbit isn't actually the case for subatomic particles.

Then again, I'm probably wrong. =P

Where's a physicist when you need one?! *hrk*

What's strange, though, is that somehow, they've found that electrons are the epitome of perfect spheres... apparently...

Subatomic particles (according to quantum mechanics) don't have an 'orbit'. Their position and velocity can't both be pinned down with indefinite precision, (heisenberg's uncertainty principle). As a result, you can't really think of an electron as something like a planet orbiting a star, and in practice a shape is used which represents a probability distribution.

(As in, it's more likely to be here, than over there, but in practice it could still be in either location.)