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Magnetisim Problem! Just need an Equation.

  1. Mar 2, 2005 #1
    Here's the problem:

    A proton follows a spiral path through a gas in a magnetic field of 0.010 T, perpendicular ot hte plane of the spiral. In two successive loops at points P and Q, the radii are 1.0 mm and 8.5 mm respectively. Calcualte hte hcnage in the kinetic energy of hte proton as it travels from P to Q/

    I just need a general direction to go in and maybe what formulas to use. Since we are trying to find kinetic energy, would I be using the (mv)^2/r for centripetal force?
  2. jcsd
  3. Mar 2, 2005 #2
    Since the measured radii are iven you can assume taht the proton moved inb perfect circles given those radii.

    so since it is moving in a perfect circle the centripetal force = magnetic force
    [tex] m \frac{v^2}{r} = qvB sin \theta [/tex]
    where theta is the angle between the particle and the field (given to you)

    solve for the unknown in that equation each time then find the change in kinetic energy
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