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Homework Help: Angular acceleration of a pulsar

  1. Mar 15, 2007 #1
    A pulsar is a rapidly rotating neutron star that emits radio pulses with precise synchronization, there being one such pulse for each rotation of the star. The period T of rotation is found by measuring the time between pulses. At present, the pulsar in the central region of the Crab nebula has a period of rotation of T = 0.19000000 s, and this is observed to be increasing at the rate of 0.00000380 s/y.

    I found the angular velocity to be 33.07 rad/s, I found this by 1/T*2PI

    Now I need to solve the angular velocity. I tried using the rotational kinematic equation:
    Wf = Wi + alpha * t

    Wf = angular velocity final
    Wi = angular velocity initial
    alpha = angular acceleration
    t = time

    Since the period of rotation is increasing by 0.00000380 s/y I added this to 0.19 and then found the Wf by take 1/.19000380 *2PI

    I used the angular velocity that I already solved for Wi, the 33.07 rad/s

    then for the time, it would be 1 year right? But does this need to be in seconds?

    So I plugged these into the equation and solved for alpha

    (Wf - Wi)/t = alpha
    (33.068rad/s-33.069rad/s)/31556926s = -3.1689x10^-11 rad/s^2

    But this is not the correct answer. Any advice?
  2. jcsd
  3. Mar 15, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Your error is in rounding off your values for W. Use many more significant figures in your calculator and you get a better estimate for the change in W.
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