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Homework Help: Confirm my answers on Oscillating Springs?

  1. Apr 24, 2010 #1
    confirm my answers on Oscillating Springs??

    Can anyone confirm or adjust my answers for problems 12 and 14? Also can someone help me start on problem 13.. Thanks guys I really appreciate the help

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

    012
    Find the speed of the block when it is 2.5 cm
    from the equilibrium position.
    Answer in units of m/s.

    013
    Find its acceleration at 2.5 cm from the equilibrium position.
    Answer in units of m/s2.

    014
    Find the time it takes the block to move from
    x = 0 to x = 2.5 cm.
    Answer in units of s.

    2. Relevant equations
    M= 0.7kg
    k= 14.7 N/m
    A= 5cm
    w= 4.58 rads/s
    T= 1.37s


    3. The attempt at a solution

    #14: x(t) = 5cm Cos(4.58rads/s*(t))
    t= (1/4.58 rads/s) cos^-1 (2.5cm/5cm) = 13.09s??
    do I convert it to meters??

    #12: E=1/2mv^2 + 1/2kx^2 = 1/2ka^2
    1/2(.7)v^2 + 1/2(14.7)(.025m)^2 = 1/2(14.7)(.05m)^2
    .35v^2=.0137
    v=0.1984m/s
    I changed the cm to m, I should have done this right??
     
  2. jcsd
  3. Apr 24, 2010 #2
    Re: confirm my answers on Oscillating Springs??

    I think I solved #13.. would I use the equation

    a = -w^2 * x???
     
  4. Apr 24, 2010 #3
    Re: confirm my answers on Oscillating Springs??

    I think that works but that is the equation for maximum acceleration. This means that equation might not always work for a problem such as this. Is acceleration always at maximum when it is half the distance from the equilibrium? (I don't know the answer to this)

    I did this problem a different way.

    https://www.physicsforums.com/showthread.php?t=397323
     
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