# Proton velocity(magnitude and direction)

1. Nov 14, 2012

### jason shaw

1. The problem statement, all variables and given/known data
A proton enters a region in which there is a magnetic field B=0.2T pointing along the positive z axis,and an electric field E=7.4 N/C pointing along the positive y axis. If we want the proton to continue travelling in a straight line without changing speed,what should its velocity(magnitude and direction) be?

2. Relevant equations

3. The attempt at a solution

2. Nov 14, 2012

### Spinnor

3. Nov 14, 2012

### Simon Bridge

Welcome to PF;
The way to get the most out of this forum is to show us your attempt at the problem - otherwise the best we can manage is to point you at some theory that will no doubt also be in your notes.

4. Nov 15, 2012

### jason shaw

I am really confused with this problem and really dont know where to start. Do I figure the two forces seperate first? Also ,I wouldnt think the proton is going to go in a straight line.

5. Nov 15, 2012

### Simon Bridge

Spinnor gave you a reference to look at - that should help.

You have a situation where there are two forces acting on an object - you know how to handle this: do a free-body diagram. Draw an arrow for the force from the B field, use that to work out which direction the force from the E field should point ... from that you can use Newton's laws to work out the magnitude.