# Homework Help: Another right hand rule test

1. Feb 4, 2014

### Tiven white

1. The problem statement, all variables and given/known data

If z is east and y is north then x is?
A. West
B. East
C. North
D. South
E. Down

2. Relevant equations
I have trued getting the proper orientation but the direction I would have obtained is not an option 'up' a comment would be appreciated

3. The attempt at a solution

2. Feb 5, 2014

### voko

Obviously, it can be either up or down. Assuming one of the given answers must be correct, that must be "down".

To see that, you would need to twist your arm quite severely. Align your middle finger (Z) with East and your index finger with South. Then your thumb will be Up. Now to make your index index finger point North as described, you would need to rotate your hand about your middle finger.

3. Feb 5, 2014

### rude man

You did not define the equation for the cross-product vector x.

If x = y x z then x is down.
If x = z x y then x is up.

EDIT: OK, never mind, you did not have "up" as one of your choices. So voko answered the question.