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Homework Help: Larmor Formula.

  1. Mar 22, 2010 #1
    1. The problem statement, all variables and given/known data

    At time t = 0 a particle of charge 'q' and mass 'm' is at a position x = 0 and has a velocity v = 0. The particle is subject to a force F = k x^(1/2) , where 'k' is a constant. Show that at time 't' the particle radiates according to:

    -dW/dt = q²k⁴t⁴ / (864)(π)(ε_0 )(c³)(m⁴)

    3. The attempt at a solution

    I first said F= ma = k x^1/2

    --> a = k x^(1/2) / m

    ---> a² = k² x / m²

    Then I substitute this into the larmor formula, but obviously this is wrong. I'm not sure where I went wrong though.

  2. jcsd
  3. Mar 22, 2010 #2


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    Homework Helper
    Gold Member

    What makes you so certain that this is wrong? Remember, the particle is accelerating along the x-direction, so its x-coordinate will be a function of time. You can find the exact form of [itex]x(t)[/itex] by solving the differential equation [itex]\frac{d^2 x}{dt^2}=a[/itex].
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