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Homework Help: Time derivatives

  1. Mar 9, 2012 #1
    1. The problem statement, all variables and given/known data

    My question is how do I take the time derivative of (theta dot)^2?

    2. Relevant equations

    3. The attempt at a solution

    Is the answer just 2(theta double dot)^1 or do you use chain rule 2(theta dot)*(theta double dot)?
  2. jcsd
  3. Mar 9, 2012 #2
    Well, assuming theta is a function of time, you must use the chain rule!
  4. Mar 9, 2012 #3


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    Science Advisor

    I take that your "dot" refers to differentiation with respect to time, t,- I will use a prime since it is simpler here- and you are asking about the derivative of [itex](\theta')^2[/itex].

    The derivative of any [itex](f(t))^2[/itex] with respect to t is [itex]2f(t)f'(t)[/itex], by the chain rule, so the derivative of [itex](\theta(t)')^2[/itex] is [itex]2(\theta')(\theta'')[/itex].
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