Angular vs linear momentum

[Robittybob1]

I'm glad it helped and I see no reason for the discouraging negative so +1.

 

No after checking carefully (since I make too many typos) this is correct.

 

All I have done is said mass times velocity and put in M (for mass) times (the dimensions I worked out earlier for velocity).

 

Is that any clearer?

Great, I see what you mean now. Did you see my post on the other thread where I had a strange result can you give me a little help please http://www.scienceforums.net/topic/88420-centrifugal-forces-appear-to-act-opposite-to-gravity-how-is-this-possible/page-24#entry868731

v/r = 2 Pi/T,

v/r = constant /T seconds, so can we call that a frequency?

 

That bit.

[studiot]

Yes that is a frequency, although your equation is an unusual rearrangement.

 

Can you also relate this to angular velocity in radians per second ?

 

Going back to dimensional analysis.

 

Work is Force times distance = (MLT^-2) x (L) = ML²T^-2

 

Potential energy is mass times height times g or M x L x (LT^-2) = ML²T^-2

 

This shows that work and energy have the same units, a useful result.

[Robittybob1]

Yes that is a frequency, although your equation is an unusual rearrangement.

 

Can you also relate this to angular velocity in radians per second ?

 

..

If something is related by 2 Pi/T does that mean it was in radians originally and is now turned back to rotations/unit time? I'll get it soon.

Hey - I'm tired now and I had a great day. Thanks.

[studiot]

Think something travelling round a circle.

 

In the time of one revolution it travels 360^o or 2[math]\pi[/math] radians or one circumference ( = 2[math]\pi[/math]r) in distance.

 

The time of one revolution is called the period.

 

Time is the linking quantity between the quantities.

 

So let us say it travels X linear units or Y angular units. (This may be more than one circle or part of one) in a time t.

 

So the objects travels n = Y/360 (degrees) or Y/2[math]\pi[/math] (radians) or X/2[math]\pi[/math]r (linear measure) revolutions in time t.

 

So the object travels n/t revolutions or cycles per second which is the definition of frequency.

 

Equally the object takes t/n seconds to complete one revolution, which is the definition of period.

Edited May 23, 2015 by studiot

[swansont]

It is the tangential component of the momentum.

Tangential being the direction perpendicular to the radial lines of a circle (curve)

The radial line is the shortest distance between them or even more basic just the distance between the two points ( a point on the circumference has a constant distance to the center point in a circle. (they are radii or radial lines maybe.)

 

No, that doesn't work. Two objects with momentum p could be moving in concentric circles of different r. They would have different angular momenta, and yet the "tangential component" would be the same.

 

The two objects could be at the same angle with respect to the origin, or be at 180º (opposite sides of the circle) but that has no effect on the magnitude of their linear momentum, or their angular momentum.

 

You idea of how this works is wrong.

[Strange]

does m = mass?

T-1 = /second or per unit time.

L what is this variable? I have seen L being used for angular momentum - what is it in your equation?

 

Perhaps you should read this: http://en.wikipedia.org/wiki/Dimensional_analysis

[Robittybob1]

 

Perhaps you should read this: http://en.wikipedia.org/wiki/Dimensional_analysis

It was a matter of understanding what the symbols meant. Thanks.