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Homework Help: Mass-spring extensions HELP

  1. Oct 9, 2008 #1
    Mass-spring extensions HELP!!!

    I'm writing a paper on one of my lab experiments and I'm not sure my physic concept is right? The question asks if the mass of a cart affects the extension of the spring. A spring is attached to a cart which is attached to sting through a pulley and connected to a hanging object of mass W (a picture is attached). From my results, the spring stretched slightly more with the cart than with out the cart attached to the spring.

    I know that at equilibrium all forces equal 0. Σ Fx = Σ Fy = 0
    Fs= kx

    (with cart)
    Σ Fx = Fs –Th
    Σ Fy = Tv + Fn - Mgw -Mgc

    (without cart)
    Σ Fx = Σ Fx = Fs –Th
    Σ Fy = Tv - Mgw

    If k is constant and Fs= kx and F=mg then mg=kx. Then if the cart was attached, mass will increase, therefore x (the spring extension) will increase, which explains why the spring stretched more when the cart was attached.

    Is this somewhat right? (I know this is wrong, because i got my paper back saying it was the wrong concept) So can you help me? Am I missing something?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
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