Multiple choice, magnetic force on the particle

1. Oct 20, 2012

Mdhiggenz

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

2. Relevant equations

3. The attempt at a solution

I know that since the charge is negative qo*Vperpendicular would be traveling in the oppsite direction. Which by the right hand rule ultimately affects B.

So using the formula F=q0V(perpendicular)*B

= 1*5(4i-3j)
= (20i-15j)

I don't understand why the answer would be D.

Or maybe my approach to the problem was incorrect?

Thanks

2. Oct 20, 2012

frogjg2003

The equation is $\vec{F}=q\vec{v}\times\vec{B}=-1C*5\hat{k}\frac{m}{s}\times(3\hat{i}-4\hat{j})T$. What is $(-1)(-4)\hat{k}\times\hat{j}$?