Proton velocity(magnitude and direction)

[jason shaw]

Homework Statement

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 traveling in a straight line without changing speed,what should its velocity(magnitude and direction) be?

Homework Equations

The Attempt at a Solution

 

[Spinnor]

You want the forces to cancel. See,

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html#c2

You want F to equal zero and you have only one variable, v.

 

[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.

 

[jason shaw]

I am really confused with this problem and really don't know where to start. Do I figure the two forces separate first? Also ,I wouldn't think the proton is going to go in a straight line.

 

[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.