# Confusion on applying right hand rule

1. Nov 23, 2013

### Genericcoder

Hi guys I always get confused when I do the right hand rule like here when I apply it to this problem I am getting different answer than what the book have.

A uniform magnetic field B, with magnitude 1.2 mT, points vertically upward throughout the volume of the room in which you are sitting. A proton with kinetic energy of 5.3 MeV moves horizontally to the north through a certain point in the room. What magnetic deflecting force acts on the proton as it passes through this point ? The proton mass is 1.67 * 10^-27 kg.

so Fb = 6.1 * 10^-15 N; the book then says the force is sideways in horzontally to the east. I am getting it pointing in the z direction even when using cross product

FB = q<v,0,0> x <0,B,0>

Fb = qvB k^ direction

2. Nov 23, 2013

### Staff: Mentor

What's your convention for relating north/south, east/west, and up/down to the x, y, and z axes? You know you've mixed something up if the force isn't perpendicular to the B field and the velocity.

(I'm assuming that you are using i,, j, and k as unit vectors in the x, y, and z directions respectively).

3. Nov 23, 2013

### Genericcoder

Ye I am using i j k as unit vectros x,y,and z directions respectively.. but I think thats what I have not relating north/south up down to x and y and z directions..

4. Nov 23, 2013