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Homework Help: Kinematics qns

  1. Jul 13, 2007 #1
    1. The problem statement, all variables and given/known data
    From eqn a=-300v^2
    Find time taken for acceleration to change from 1.50ms^-1 to 0.75ms^1

    2. Relevant equations

    3. The attempt at a solution

    I tried integrating, but still cannot get the ans.
  2. jcsd
  3. Jul 13, 2007 #2
    This is a simple differential equation. Try separation of variables.
  4. Jul 13, 2007 #3


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    JohnDuck is quite right, except I think the usual term is 'separable' rather than 'separation of variables'. And it is fairly easy. You'll just have to be clearer to us where you are confused.
    Last edited: Jul 13, 2007
  5. Jul 14, 2007 #4


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    "separable' is the adjective, "separation" the noun. Yes, this is a "separable" equation and the technique for solving is "separation of variables"- you are both right.

    lycheeliang, you have dv/dt= -300v2 so, separating the variables (the verb form!) you have dv/v^2 = -300dt. Integrate both sides of that.
  6. Jul 14, 2007 #5
    oh thanks!
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