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: Combination of 3 springs at given angles

  1. Jan 26, 2010 #1
    Three springs of spring constant kare connected to a body of mass m and rigid supports, so that the angles are
    A 90 degrees between two and 135 degrees between each of these two and the third.
    B 120 degrees between any 2 adjacent ones.
    Find time period of vibration.
    I worked out a method to solve this question. I added 2 of the spring constants vectorially, first dividing each by the cos of half of the angle between them (45 and 60 degrees) and the third simply as k to get a net spring constant. This gave a correct answer but I don't remember what logic I used and it may not have been correct. Could someone show me the correct solution?
    diagram
    http://i898.photobucket.com/albums/ac182/watermlon/df.jpg
     
    Last edited: Jan 26, 2010
  2. jcsd
  3. Feb 4, 2010 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi watermlon! Welcome to PF! :smile:

    What matters is the components of force in each direction.

    If the extension vectors are x y and z (these are not coordinate directions), then the forces are k1x + k2y + k3z

    in this case, k1 = k2 = k3 = k,

    so the total force is k(x + y + z), and you correctly took components along an axis of symmetry (the total of components along the perpendicular axis would be zero). :wink:
     
  4. Feb 6, 2010 #3
    Thanks, tim. I understand it now.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook