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: Pendulums with Mechanical Energy (conical pendulum?)

  1. Jul 22, 2011 #1
    1. The problem statement, all variables and given/known data

    The pendulum bob in Figure 6.11 must circle
    the rod interrupting its swing, and the string
    must remain taut at the top of the swing. How
    far up must the bob be raised before releasing
    it to accomplish these goals?


    2. Relevant equations

    Potential Energy = mgh
    Kinetic Energy = 1/2mv^2
    mgh = 1/2mv^2

    3. The attempt at a solution

    I'm still unclear with what the question is asking for or how I'm suppose to solve it; though I'm guessing it deals with the conversion of kinetic energy into gravitational potential energy and maximum height. How the rod play into the question, or what the distance from the rod to the pendulum bob means, I've no idea. This sounds awfully similar to a conical pendulum, which a quick wikipedia search showed as pretty complicated.
    So, how do?
  2. jcsd
  3. Jul 22, 2011 #2


    User Avatar
    Science Advisor
    Homework Helper

    When the string hits the rod, it the bob will start circling the rod in a 10 cm radius circle. It won't reach the point 10 cm above the rod unless you release it from high enough. How high is 'high enough'?
  4. Jul 26, 2012 #3
    Here is the Solution for you: Please click on the image. For more questions plz send requests here....

    Attached Files:

    • Pics.jpg
      File size:
      17.2 KB
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook