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Homework Help: Mechanical energy of a mass-spring system

  1. Apr 4, 2005 #1
    Hey,
    Stuck on finding the mechanical energy of a mass-spring system, my question is as follows > A mass-spring system oscillates with an amplitude of .026 m. The spring constant is 290 N/m and the mass is 0.50 kg, it asks for the mechanical energy in (J). and the maximum acceleration of the mass-spring system which is 15.08 m/s (verified, webassign rules).

    Mechanical energy is confusing to me, I am pretty determined it might be potential(PE)enery + kinetic energy(KE), but ofcourse the formula for KE involves velocity. I only have the acceleration so I feel I have gone astray along the way.

    Basically I am having trouble finding where to start and then I'm wondering how to get the answer in Joules.

    Thanks.
     
  2. jcsd
  3. Apr 4, 2005 #2
    The mechanical energy of a mass-spring system with speed v at position x is [tex] E = .5mv^2 + .5kx^2 [/tex] .

    Pick a point in the oscillation and apply this equation. (Hint: there's a special point in its motion which simplifies this problem greatly).
     
  4. Apr 4, 2005 #3
    Thanks for the reply. I assume when you say pick a point you mean pick a point to plug in for the variable V. The amplitude is .026m

    So far I have this

    E=.25v^2 + 0.09802

    Would V be 1/2 of the maximum acceleration?
     
  5. Apr 4, 2005 #4
    When the mass it as its maximum displacement what is its velocity? You should know this without having to use a formula. If you don't, review the chapter.
     
    Last edited: Apr 4, 2005
  6. Apr 4, 2005 #5
    :bugeye: The chapter has been read very carefully by me twice. We haven't really covered mass at its maximum displacement, or maybe we have and called it something else.

    I think by maximum displacement you mean the amplitude which is ofcourse .026m. Maximum accel. is 15.08 m/s . I realize the answer is probably smack in front of me but with only one submission left on web assign I remain wary. I still am a bit confused at how to find the velocity with mass, amplitude, max. accel, and 290N/M.
     
  7. Apr 4, 2005 #6
    Wow I am stupid!
    KE= 1/2 290 N/m * (.026)^2

    Thanks!
     
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