# Do pseudo vectors have anything to do with motion?

1. Aug 24, 2013

### jaydnul

... or are they there just to help the calculations? I mean since torque can arbitrarily be shown to go in opposite directions depending on if you use the right hand rule or left hand rule (i know this isn't really used but from what i understand it would work out the same), it wouldn't have a physical effect in the translational motion, right?

Also, just a refresher, are all angular quantities considered to be pseudo vectors? Angular velocity, angular displacement, angular acceleration...?

2. Aug 24, 2013

### 'roidbreaker

"angular quantities" are just abstractions that prequire special conditions to facilitate some computations. so yes, they are arbitrary, but they are mostly consistent and make it easier to do standard stuff. in most cases they are the analogues of the integral of the of the continuous function multiplied by the heaviside abstraction of the definition.

I personally prefer to work with the continuous vector lists so I don't deal with that crap.

of course I could always be lying.

3. Aug 25, 2013

### jaydnul

Ok. I was watching a video that was explaining why gyroscopes precess and he was showing it in terms of the angular momentum vector and the torque vector. But since those vectors are arbitrary, why did it precess in one direction and not the other?

4. Aug 25, 2013

### eigenperson

It turns out that whichever way you choose to define the direction of the torque vector, the analysis ends up with the gyroscope precessing the same way. If you repeat the analysis using the "left-hand rule" instead of the right-hand rule, you'll see this.

Note that the choice of the torque vector entails the choice of the angular momentum vector, so there is really only one choice to make. Whichever choice you do make, any vector quantities with direct physical significance, like force and velocity, end up coming out the same.