# Homework Help: Proton In A Magnetic Field

1. Apr 30, 2006

### tmth

I've got two homework questions I don't really understand. Coming to the end of the year so my teacher is rushing through things and forgetting to give us all the notes we need..
I think I need an equation to solve both of em, but I don't know what. Help/an explanation on how to do the problem is greatly appreciated. ^_^

#1) A proton moves at right angles to a magnetic field of .124 T with a speed of 2.3x10^7 m/s. Find the magnitude of the acceleration of the proton.

#2) A proton moves eastward in the plane of Earth's magnetic equator so that its distance from the ground remains constant. Assume the Earth's magnetic field at the equator is 3.23 x 10^-5 T. The acceleration of gravity is 9.8 m/s^2. What is the speed of the proton?

2. Apr 30, 2006

### nrqed

Have you covered ${\vec F} = q {\vec v} \times {\vec B}$? That is all that is needed (this equation means that the *direction* is given by the right hand rule and the *magnitude* of the force is the absolute value of the charge times v B sin (theta) where theta is the angle between the velocity vector and the magnetic field. This is all you need.

3. Apr 30, 2006

### tmth

@_@ Haven't covered that.

4. Apr 30, 2006

### nrqed

:surprised Then it is very strange that he expects you to do those problems if you haven't even seen the basic equation needed!!! I unfortunately don't have the time right now to explain it in details. You shoudl look at your textbook, I am sure they show examples!!

5. Apr 30, 2006

### tmth

Well, the problems come from an online problem set, and my teacher doesn't really look at the specific problems. And it *is* optional, but I want to do it to help my grade...
I got em right, with further help from the textbook. Thank you!