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

First Order Differential Equation Problem

  1. Oct 21, 2008 #1
    1. The problem statement, all variables and given/known data
    A 14 lb weight attached to the end of spring stretches it 4 in. Find the equation of motion if the weight is released from rest at a point 3 inches above equilibrium position

    2. Relevant equations

    3. The attempt at a solution

    ok I need some help just finding out what the k constant is. I know I use hooks Law F=kx, and F is mg=kx. Do i consideer equilibrium when nothing is attached to it, and that is y=0? Then what is the x considered in Hooks Law equation mg=kx , is it the distant its stretched from equilibrium position ?

  2. jcsd
  3. Oct 21, 2008 #2
    First, this is a undamped second order problem.

    I would consider equilibrium is when mg=kx.

  4. Oct 21, 2008 #3
    now what do u mean by equillibrium, is that when its unstretched and no wait? or the differecne between unstretrched and stretches in the middle in other words ?
  5. Oct 21, 2008 #4
    when the spring is stretched (downward) to x_0 such that kx_0=mg, it's equillibrium, that's y=0.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook