## Physics Olympiad 29

noospace
Posts: 46
Joined: Fri Feb 22, 2008 9:14 pm

### Physics Olympiad 29

I can't understand why the answer is E.

The velocity with which the ion enters the magnetic field is determined by

1/2 m v^2 = q V

ans so v is proportional to sqrt(q/m).

The radius of the arc in a magnetic field of strength B is proportional to (m * v) /q which is proportional to sqrt(m/q).

Since the oxygen is double the charge and quadruple the mass, we expect oxygen to have a radius which is increased by a factor of sqrt(2)

blackcat007
Posts: 378
Joined: Wed Mar 26, 2008 9:14 am

### Re: Physics Olympiad 29

noospace wrote:http://www.princeton.edu/~jdpeters/docs ... piad99.pdf

I can't understand why the answer is E.

The velocity with which the ion enters the magnetic field is determined by

1/2 m v^2 = q V

ans so v is proportional to sqrt(q/m).

The radius of the arc in a magnetic field of strength B is proportional to (m * v) /q which is proportional to sqrt(m/q).

Since the oxygen is double the charge and quadruple the mass, we expect oxygen to have a radius which is increased by a factor of sqrt(2)
yes even i have this same problem.. i think there is a mistake with the answer key

noospace
Posts: 46
Joined: Fri Feb 22, 2008 9:14 pm

### Re: Physics Olympiad 29

Okay. That's a relief. I thought I was going crazy.