1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A quick dirivative Question

  1. Apr 28, 2006 #1
    Alright, I'm doing a dynamical magnetism problem for my physics class. I've got it almost done except I need to take the derivative of 1/x^3 with respect to time. X in this case is a variable for meters, I want to turn this into an expression with velocity (Velocity is given) but I'm not sure what that is.

    d(1/x^3)/dt = ? I'm pretty sure its not just 1/v^3 but that would be nice ^_^. Any help would be appreciated.

    Would this just be -4x^-3*v?
    Last edited: Apr 28, 2006
  2. jcsd
  3. Apr 28, 2006 #2


    User Avatar
    Homework Helper

    No, you differentiated wrongly. What is [tex]\frac{d}{dx}(x^{-3})[/tex] ?

    Then [tex]\frac{d}{dt}(x^{-3}) = \frac{d}{dx}(x^{-3})(\frac{dx}{dt}) = v\frac{d}{dx}(x^{-3})[/tex] as you correctly surmised.
  4. Apr 28, 2006 #3
    k, I guess I have a bigger problem then originally thought since X is not given :/.
  5. Apr 28, 2006 #4


    User Avatar
    Homework Helper

    What ? :confused:

    x is a variable denoting displacement right ? And don't mix up the cases - stick to small x.

    All I'm saying is you differentiated wrong.

    What is [tex]\frac{d}{dx}(x^n)[/tex] ? This should be in the textbook. Now plug in n = -3.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: A quick dirivative Question
  1. Quick questions (Replies: 2)

  2. Quick questions (Replies: 1)

  3. Quick question (Replies: 5)

  4. Quick Question (Replies: 10)

  5. Quick question (Replies: 1)