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: Maximum kinetic energy of a pendulum

  1. Jul 3, 2011 #1
    1. The problem statement, all variables and given/known data
    Okay, so I'm using the online Giancoli physics thing for AP Physics C summer work (see: "([PLAIN]http://wps.prenhall.com/esm_giancoli_physicsppa_6"[/URL]. [Broken] I think my way of doing it is correct, but the online checker says I'm wrong.
    The question: "A pendulum has a mass of 3.2 kg, a length of 1.5 meters, and swings through a (half)arc of 17 degrees. To the nearest tenth of a Joule, what is its maximum kinetic energy of the pendulum?"

    2. Relevant equations
    PE = mgh
    KE = 1/2mv^2

    3. The attempt at a solution
    Find the PE of the pendulum. The height of it at 17 degrees: .43856 meters (about).
    PE = 3.2*9.81*.43856 = 13.767 Joules. But the online checker says 2.1 Joules.

    What am I doing wrong? Or, am I doing it right, the online thing is just wrong?



    Attached Files:

    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Jul 3, 2011 #2


    User Avatar

    Staff: Mentor

    Your height for the pendulum bob is not correct.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook