# Finding the radius of a Proton's arc inside a square.

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1. Oct 19, 2015

### RelativeJosef

1. The problem statement, all variables and given/known data
This is for a practice question on an exam:

I am able to finish the problem, if I could figure out how to find the radius of this arc the proton makes.

2. Relevant equations
I have nothing.

3. The attempt at a solution
I have tried arc length equations and just integrating the change in dx and dy, but all my answers have been nonsensical.

I have a feeling this is very simple and I wasn't paying attention enough in Geometry back in grade school.

Any help would be greatly appreciated.

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2. Oct 19, 2015

### Staff: Mentor

Please write out the complete problem statement.
Surely the radius of the arc is trivial by inspection of the image?

3. Oct 20, 2015

### RelativeJosef

I have since deduced the radius, and indeed it was trivial.

If you are interested, in calculating the required magnetic field of this square magnet to produce such a curve in a protons path through the magnetic field, the radius is simply the side length of one side of the square.