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Ranking velocities of particles in uniform magnetic field 
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#1
Mar1210, 05:20 PM

P: 190

1. Five equalmass particles (A–E) enter a region of uniform magnetic field directed into the page. They follow the trajectories illustrated in the figure.
Rank from largest to smallest velocity 2. qvBsin(theta) = ma qvB = ma = m(v^2/r) v = qBr/m 3. Based on their radii, it should be A > B > C=E But what about D? It is neutral, so has no radius because it doesn't go in a circle, but clearly has a velocity despite r = 0. Is the answer indeterminate, then? 


#2
Mar1210, 07:44 PM

HW Helper
P: 2,322

I think you're meant to assume that all particles have the same charge; otherwise, the problem would be unsolvable. So assuming they have the same charge, D appears to go straight because it's barely affected by the magnetic field. What does that tell you about its velocity?



#3
Mar1210, 09:43 PM

P: 190

The answer actually was that it couldn't be determined.
Now I am asked to rank the speeds largest to smallest of A, B, C, and E. I thought it was clearly A > B > C=E, but it is not and it tells me this: The radius of the trajectory of a particle depends on more than just its speed. Be sure not to make assumptions about the relative magnitudes of the charges. WTF? 


#4
Mar1310, 08:27 AM

Mentor
P: 12,069

Ranking velocities of particles in uniform magnetic field



#5
Apr411, 05:14 PM

P: 1

nvmm



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