What is the ranking of particle speeds in a constant magnetic field?

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Homework Help Overview

The discussion revolves around the ranking of particle speeds in a constant magnetic field, focusing on three particles with identical charges and masses that follow different paths. Participants are analyzing the relationship between the radius of the circular paths and the speeds of the particles.

Discussion Character

  • Conceptual clarification, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are questioning the validity of the book's answer (2-3-1) and exploring the implications of different radii on particle speed. Some suggest that larger radii indicate higher speeds, while others argue about the forces acting on the particles and how they relate to their velocities.

Discussion Status

The discussion is ongoing, with multiple interpretations being explored. Some participants assert that the correct ranking should be 1-3-2 based on their reasoning about forces and radii, while others are seeking confirmation of their understanding and the reasoning behind the book's answer.

Contextual Notes

There is a noted assumption that the magnetic field strength is constant, but participants are debating the implications of differing radii on the forces and velocities of the particles. The discussion reflects uncertainty regarding the relationships between force, radius, and speed in the context of magnetic fields.

Suy
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Homework Statement


http://img19.imageshack.us/img19/3505/picture1ul.jpg
Three particles have identical charges and masses. They enter a constant magnetic field and follow the paths shown in the drawing. Rank the speeds of the particles, largest to smallest

Homework Equations


r=(mv)/(qB)

The Attempt at a Solution


the book give me 2-3-1, but isn't that the larger the radius , the faster the particles is?
can someone explain it?
ty
 
Last edited by a moderator:
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i guess 2-3-1 is wrong, because they are assuming that 1,2,3 radius is same,
if radius same F=qBv or F=(mv^2)/r, 1 have the lowest magnetic downward force or centripetal force, so if low force, less velocity, this is why 1 will be the slowest.
But if they all have the same force, using this r=(mv)/(qB), (large radius, great speed),because in the diagram they have different radius, so we can't assume they are the same, we can only assume that the force is same, so it would 1>3>2
am i right?
 
No, I'm afraid you're talking nonsense. As the question stated, the only thing that's constant for all 3 particles is the magnetic field strength, or B. The particles experience different forces because they trace out circles of different radii, and F=mv^2/r.

2-3-1 is wrong; the actual answer should be 1-3-2. As the OP noted, the faster the speed, the larger the radius.
 
o , i mean the book give me 2-3-1, i was just wondering why the answer is 2-3-1
the book also stated that "Great Force ,Great velocity"
 
But 2-3-1 is NOT correct. The answer should be 1-3-2.
 
http://img132.imageshack.us/img132/9773/81045485.jpg
Can you tell me if this is right?
1) B
3)C<B<A
For the first one, my friend said it's A,because it bends more,
i think he is wrong...
If i am wrong, please explain it
ty!
 
Last edited by a moderator:
anyone?, i need someone to confirm my answer...
TY!
 

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