1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Particle Roundabout

  1. Nov 7, 2015 #1
    1. The problem statement, all variables and given/known data
    The figure shows 11 paths through a region of uniform magnetic field. One path is a straight line; the rest are half-circles. The table gives the masses, charges, and speeds of 11 particles that take these paths through the field in the directions shown. Which path in the figure corresponds to which particle in the table?
    hrw7_28-31.gif
    image002.gif

    2. Relevant equations
    r = (mv)/(qB)

    3. The attempt at a solution
    I don't know how to use that equation to get the answer but I know particle 11 should be k. What tells how big the semi circle is and where it starts?
    Please help! Thank you!
     
  2. jcsd
  3. Nov 7, 2015 #2

    phyzguy

    User Avatar
    Science Advisor

    You have an equation for the radius in terms of m, v, q, and B. The problem gives you m, v, and q. You don't know B, but you can assume that it is the same for all of them. So you should be able to determine the relative values of r for all of the particles. In other words, if two particles have the same m and q, but different v's, how will the two radii compare?
     
  4. Nov 7, 2015 #3
    I got
    Particle 1: 2R
    Particle 2: R/2
    Particle 3: R
    Particle 4:8R
    Particle 5:4R
    Particle 6:-2R
    Particle 7:-R/4
    Particle 8:-R
    Particle 9:-8R
    Particle 10:-4R
    Particle 11: --

    But I can't tell if where the particles enter the semicircle tells whether or not the particle is negative/positive? And finding the radius finds the size of the semicircle right?
     
  5. Nov 7, 2015 #4

    phyzguy

    User Avatar
    Science Advisor

    OK, this is a good start. Positive particle will curve in one direction, negative particles will curve in the other direction. You don't know B, so you don't know which is which, but do you see that some particles are circling clockwise and some circling counter-clockwise? Also, it is not true that the radius finds the "size" of the particle - the radius is determined by m, v, and q.
     
  6. Nov 7, 2015 #5
    Since the smallest semicircle size is -R/4 particle 7 path d? So negative particles go clockwise and postive particles counter clockwise
     
  7. Nov 7, 2015 #6

    phyzguy

    User Avatar
    Science Advisor

    Makes sense to me - keep going.
     
  8. Nov 7, 2015 #7
    Thank you so much! I got it :D
     
  9. Nov 8, 2015 #8

    phyzguy

    User Avatar
    Science Advisor

    You're welcome. Glad I could help.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Particle Roundabout
  1. Particle movement (Replies: 21)

  2. Spiraling particle (Replies: 15)

  3. Particle in space (Replies: 8)

  4. Statics of Particles (Replies: 7)

  5. Particle collision (Replies: 8)

Loading...