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Speed of Change

  1. Mar 7, 2006 #1
    I was just thinking that whether changes have any speed.
    Suppose we have a system in which a bodyA is rotating around an other body B through centripetal force. If B gets an instantaneous hit so that its position changes. Then what will be the speed of change or effect or whatever with which the displacement of B is communicated to A:confused:
  2. jcsd
  3. Mar 7, 2006 #2
    The speed is c.

    All electric, magnetic, and gravitational fields move at c.
  4. Mar 7, 2006 #3
    Which translates into: If B were the Sun and it suddenly exploded at this very moment, and A were the Earth, then we wouldn’t experience any gravitational effects for another 8 minutes.
  5. Mar 8, 2006 #4


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    Sure the speed of change can change. In classical physics, the speed of change is called acceleration - a first order [linear] change in speed v time. But the rate of change need not be linear, nor is it unphysical - in roller coaster design it is routine to consider second order changes in the speed of the speed of change. The technical term for this is 'jerk'. In geometry this can be compared to the difference between the area of a circle and volume of a sphere.
    Last edited: Mar 8, 2006
  6. Mar 13, 2006 #5
    Chronos, I'm really surprised that such a thing like speed of change existed theoretically. But, why is there a limit (c) to this speed. Can't it be instantaneous.
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