# Homework Help: Magnetostatics multiple choice

1. Apr 17, 2012

### goomer

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

A charged particle traveling with a velocity v in a magnetic field B experiences a force F that must be:

A. parallel to v
B. perpendicular to only v
C. parallel to v-B
D. parallel to B
E. perpendicular to v x B

2. Relevant equations

Requires this right hand rule, I believe:

3. The attempt at a solution

Looking at the diagram, I'd say that the force should be perpendicular to both the force and the velocity and I had originally picked E. E is not correct, so would the right answer be B? But that would mean that force is not perpendicular to v and it very clearly is....

2. Apr 17, 2012

### collinsmark

Are you sure you copied down the problem correctly? Including the choices? The answer isn't E, but it's not quite any of the other others either, as they're presently written.

3. Apr 17, 2012

### tiny-tim

goomer, can you check the wording of C ?

4. Apr 17, 2012

### goomer

Oh sorry! C should be "Parallel to vxB".

I assume is C is the right answer then? If so, why?

5. Apr 17, 2012

### collinsmark

Maybe this will help.
http://en.wikipedia.org/wiki/Cross_product

6. Apr 18, 2012

### tiny-tim

from the pf library
The cross product of two vectors $\mathbf{A}$ and $\mathbf{B}$ is a third vector (strictly, a pseudovector or axial vector) $\mathbf{A}\times\mathbf{B}$ perpendicular to both of the original vectors …