Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Related rates?

  1. Nov 13, 2004 #1

    Is this a question on related rates? If so, can anyone help me do this question? I have no clue on even how to start it out.

    A clock has an hour hand 4cm long and a minute hand 8cm long. How fast is the distance between the tips of the hands changing at 2:00?
  2. jcsd
  3. Nov 13, 2004 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    1. Describe the position vectors of the tips as follows:
    [tex]\omega_{h},\omega_{m}[/tex] are the respective angular velocities (you should be able to figure them out by yourself).
    [tex]\theta_{h,2},\theta_{m,2}[/tex] are the respective angles made to the positive x-axis (that is, 3 o'clock) at time 2.00

    2. The distance vector [tex]\vec{d}(t)[/tex] fullfills:
    The distance, d(t) fullfills:
    [tex]d(t)=||\vec{d}(t)||[/tex] that is, the LENGTH of the distance vector.
    3. The separation velocity is therefore given as:
  4. Nov 14, 2004 #3
    Thanks for your hlep
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook