1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Elephant in the way kinetic energy problem.

  1. Oct 10, 2007 #1
    "Elephant in the way" kinetic energy problem.

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

    I found this on one of those "OMG FUNNY" internet web pages. I am trying to attempt a solution.

    2. Relevant equations

    Mechanical energy is conserved so Einitial=Efinal. Uinitial+Kinitial=Ufinal+Kfinal.

    3. The attempt at a solution

    KE+PE = Total Energy. When the 3kg object is released from a 5m. I am unsure on how to procede with this problem. How does the force constant k of the spring factor into the solution?
    Last edited: Oct 10, 2007
  2. jcsd
  3. Jun 10, 2008 #2
    You're doing it wrong.
    How to do this problem:
    U(initial) {which is gravitational potential energy} = mgh, where h is 5m, m is 3kg, g is 9.81m/s^2.
    U(final) {which is elastic potential energy} = 1/2kx^2, where k is 100.
    WE WANT X.
    W=delta E
    Conservation of energy in sys mass, plane, earth. W=0
    0=1/2kx^2 - mgh
    So, x=Square Root ((2mgh)/k)
    So, the answer in this problem is SqRt((2(3kg)(9.81m/s^2)(5m))/100)
    ~SqRt 3 = 1.73205 meters

    Hope that helped, if you care at this point, months later.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Elephant kinetic energy Date
Momentum and Kinetic Energy Tuesday at 2:35 PM
Lifting an elephant with a pulley & rope May 21, 2015
30,000 fleas jumping off an elephant Mar 31, 2014
Find the force needed to move the elephant Oct 10, 2012
Newtons Laws with mouse and elephant Feb 25, 2009