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!

Rate of change problem very hard please help

  1. Oct 2, 2008 #1
    Rate of change problem...very hard...please help!!!

    1. The problem statement, all variables and given/known data
    The hands on a clock are of length 5 inches(minute hand) and 4 inches(hour hand). How fast is the distance between the tips of the hands changing at 3:00?

    3. The attempt at a solution

    Let the coordinates of the two hands be (x1,x2) for the minute hand, and (y1,y2) for the hour hand. Then,

    s(distance) = sqrt((x2-y2)^2 + (x1-y1)^2)

    Also,

    25=(x1)^2 + (x2)^2
    16=(y1)^2 + (y2)^2

    Then ds/dt = (-2(x1 - x2y1/y2)dy1/dt - 2(y1 - y2x1/x2)dx1/dt)/sqrt((x2-y2)^2+(x1-y1)^2).
    But I don't know how to calculate these rates.

    Please Help!!!
     
  2. jcsd
  3. Oct 3, 2008 #2
    Re: Rate of change problem...very hard...please help!!!

    The problem involves things in a circular motion. I would convert x and y into parametric values involving sine and cosine with an angular velocity. That should tell you all those rates you don't know.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Rate of change problem very hard please help
  1. Help! rates of change (Replies: 22)

Loading...