# Homework Help: Qvxb maybe not?

1. Apr 11, 2009

### SoulofLoneWlf

qvxb maybe not??

1. The problem statement, all variables and given/known data
consider the example of a positive charge moving in the -z direction with speed with the local magnetic field of magnitude in the +z direction. Find , the magnitude of the magnetic force acting on the particle.
Express your answer in terms of , , , and other quantities given in the problem statement.

2. Relevant equations

f=qvXb yet this does not work ;/
This would be true if and were orthogonal. Instead, they are antiparallel--look back at the definition of the cross product if you still have trouble.
3. The attempt at a solution

2. Apr 11, 2009

### Staff: Mentor

Re: qvxb maybe not??

$$\vec{F} = q\vec{v}\times \vec{B}$$

works just fine, but that only equals qvB when v and B are orthogonal.
Sounds like good advice to me.

3. Apr 11, 2009

### SoulofLoneWlf

Re: qvxb maybe not??

thank these things just confuse me at time :) lol easy to study for hard to do some how :/