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!

Mass and springs problem

  1. Oct 3, 2004 #1
    suppose that the two springs have different spring constants k1=280 N/m and k2=260 N/m and the mass of the object is m=14 kg. Find the frequency of oscillation of the block in Hz.

    the first picture on this site is what the problem looks like. Its a mass between two springs that are attached to walls.

    i know that angular frequency equals the square root of k/m. but i don't know how to do it when there are two springs involved. Please help Asap. Thanks so much
  2. jcsd
  3. Oct 3, 2004 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Welcome to PF!
    Let your origin be at where both springs has their rest length.
    If you displace the box a distance "x", what are the forces (with direction) acting on it from either box?
  4. Oct 3, 2004 #3
    So if i have F1= -kx = -280x and F2= 260x do i then add them ? if so i would get Ft= -20x ...then should i use -20 as my value for k? and substitute it into the equation that i said before...where frequency equals the square root of (k divided by m)?

    THanks so much for your help by the way...this forum is a wonderful idea and i am definately going to spread the word!
  5. Oct 4, 2004 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    No that is incorrect!
    Let the rest lengths be [tex]L_{1},L_{2}[/tex]
    For clarity, "x" be a positive number.
    Then, the new length of spring 1 is [tex]L_{1}+x[/tex]
    Hence, [tex]F_{1}=-k(L_{1}+x-L_{1})=-kx[/tex]
    Let's look at spring 2:
    If spring 2 had been lengthened by a positive amount "y" (dragged out to the left), then, the force from it would drag the block to the right (the positive direction).
    Hence, for positive displacement of spring 2 "y", [tex]F_{2}=2ky[/tex]
    Now, setting y=-x (spring 2 is actually shortened), we get:

    Hence, total force F on block is:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Mass and springs problem