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Homework Help: Oscillatory motion

  1. May 2, 2004 #1
    Hey can someone guide me in the right direction here.

    Q. Show that the time rate of change of mechanical energy for a damped , ubdriven oscillator is given by dE/dt=-bv^2 and hence is always negative.
    Proceed as follows: Differentiate the expression for the mechanical energy of an oscillator, E=1/2mv^2 + 1/2kx^2. And use this equation:
    -kx-b(dx/dt)=m(d^2x/dt^2)
    I know it tells you how to approach the question and all, but I guess the main problem is that my differentiation isn't that great.
    Anyway for the Energy equation I was thinking that you could change the v to change in x over change in time. delta(x)/delta(t)
    not sure though.
    Any help would be appreciated.
     
  2. jcsd
  3. May 2, 2004 #2
    nevermind :)
    It was easy, it's just that I made a small error at the beginning that through me off a bit.
     
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