# Homework Help: Need help with a electromagnetism question

1. Jun 4, 2010

### Gardalay

A stone is moving constantly in a horizontal motion in a uniform magnetic field in the direction pointing into the page. The field's strength is 1.7T. How fast does the stone have to move in order for it to remain moving horizontally without any vertical deviation?

For this quesion, using (9.8)(mass of rock)=QvB doesn't work because there's no vertical deviation. I also tried to do mv^2/r=QvB, but since it is moving horizontally and not in a circle, that doesn't work either. Can someone help me with this question please.

2. Jun 4, 2010

### ehild

Is that stone charged? What is its charge? Is the page vertical?

Do you know the meaning of the letters in the equations you cited? Is any of them include "vertical deviation"?

ehild

3. Jun 4, 2010

### Gardalay

yeah i know the letters...the charge is -0.010C, my page is not vertical...

4. Jun 4, 2010

### ehild

What is the direction of the magnetic field? You said, it is pointing into the page. Which page? Show a picture.

ehild