# Right hand rule for Spinning things

1. Dec 2, 2007

### Forgetful_Duck

Right hand rule for Spinning things....

Hi, I'm havign a hard time figuring out how the right hand rule works for Angular momentum, Angular velocity and torques.

Its so confusing because At university we get problems about rotating solid bodys like a disk on a rod, and when the question specifies the wheel direction as Clockwise and or anti clockwise, spinning on a horizontal axis.
I am not sure from WHICH point of view is the axis clock or anti clockwise.

When you look at a spinning object, being clock or anti clock depends on which side you look at it from....

Which also comes to my next confusing dilema.

If the direction of clock or anti clock depends on which side the obserevr views then using the right hand rule, doesn't that give 2 completely different sets of answers for angular velocity, anuglar momentum and torque?

Am i confusing anyone yet?

Can someone pelase explain to me how i should apply the right hand rule to find vector direction of velocity, anuglar momentum and torques!

Thanks

2. Dec 2, 2007

### rcgldr

As long as you use the same orientation, when doing the problem it won't matter.

Right hand rule means that if an object is rotating counter-clockwise, with the axis pointed at you, then the angular vector will point at you. With right hand rule, orient your palm so that the objects rotation is in the same direction that your fingers go from open to close, with your palm so oriented, the angular vector points in the direction of your thumb.

3. Dec 3, 2007

### Forgetful_Duck

Then what about the Direction of Torque and angular momentum?

Angular momentum is in the same direction as angular velocity?

But how does that work when L = r x p , shouldn't it be perpendicular?

4. Dec 3, 2007

### rcgldr

Treated the same as angular velocity, with right hand rule.

r and p lie on a plane, and the angular vector is always perpendicular to this plane, via right hand rule.

5. Dec 3, 2007

### Forgetful_Duck

Ah!!!

Thanks, this makes a lot more sense now.

I was under the impression that the 3 were related by the right hand rule like how Force, Field, and Direciton of current were related via the right hand rule in the topic of Electric and Magnetic Fields. Where you use 3 finegrs of the right hand, thum = current , fore finger field and rude finger force. lol

Thanks for cleaing this up.