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Homework Help: Particle through magnetic field

  1. Dec 16, 2014 #1
    1. The problem statement, all variables and given/known data
    A particle enters perpendicular to a magnetic field with a speed of 100,000 m/s. The magnetic field has a strength (B) of 0.80 T. The particle starts doing a spinning motion with an 0.1m radius. The particle charge is +3e (three elementary charges). Calculate the mass of the particle.

    2. Relevant equations
    Since it does a spinning motion, we need the formula for centripetal motion. F=m(v^2/r). We also need a formula that gives us F based on B and Q (charge) and v (speed). For that we have F = QvB.

    3. The attempt at a solution
    We set them equal.

    m(v^2/r)=QvB and we can take off one v.
    m(v/r)=QB, we move the things around so we have m alone
    m*v = rQB => m = rQB / v

    We enter everything that is known and we get:

    0.1 * (3*1.6*10^-19) * 0.80 split by 100,000.

    Result: 3.84 × 10^-25 kg. Am I correct?
  2. jcsd
  3. Dec 16, 2014 #2
    Before we answer your question, do you think you are correct?
  4. Dec 16, 2014 #3
    I do!
  5. Dec 16, 2014 #4
    Ok, actually whenever you believe you are correct, you should just be confident and not doubt yourself.
    You are correct in this question!
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