1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Related Rates and Circles

  1. Nov 7, 2013 #1


    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data

    The circumference of a circle is increasing by 4 inches per second. What is the rate of change of the diameter with respect to time if the radius is 2 inches?

    2. Relevant equations

    C = 2∏r = ∏d.

    3. The attempt at a solution

    dC/dt = 4 = ∏dd/dt.

    dd/dt = 4/∏

    Is this it? It seems as if the information given about the radius is irrelevant.
  2. jcsd
  3. Nov 7, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi Qube! :smile:
    yup! :biggrin:
  4. Nov 7, 2013 #3


    Staff: Mentor

    Yes, this is it. The circumference is a constant multiple of the diameter, so the rates of change of circumference and diameter are also going to be constant multiples of one another.
  5. Nov 7, 2013 #4


    User Avatar
    Gold Member

    Alright, thanks guys. Thanks for the explanation; this provides an easy way to check!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted