# Angle between magnetic field B and velocity of charge

## Homework Statement

Find magnitude and direction of F of a charge moving through a magnetic field.

velocity: 5 m/s
charge: 2 C
B: 3 T (pointing out of the page when drawn)

## Homework Equations

(vector)F=qv x B
(magnitude)F=qvBsinθ

## The Attempt at a Solution

I know to use the equation for magnitude but I'm confused as to what the angle would be between v and B. Since the magnetic field is pointing out of the page, would the angle be 90°, making sin(90)=1?

Also, don't know what direction that would be. Since I don't know the direction of B, I'm not sure how to use the right hand rule to figure this out.

## The Attempt at a Solution

rude man
Homework Helper
Gold Member
You do know the direction of B. It's out of the page.

Unfortunately, the problem does not define the direction of v so you can't solve it.

Sorry, forgot to mention that: the velocity moves straight from left to right.

rude man
Homework Helper
Gold Member
Sorry, forgot to mention that: the velocity moves straight from left to right.

OK, so place a sheet of paper on the table, draw an arrow from left to right = v, then hold a pencil at the back end of the arrow pointing straight up (B).
What is the angle between the arrow and the pencil?