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: Spring SMH

  1. Nov 19, 2006 #1
    Question: A block of mass .05 kg is pulled .3 m from its equilibrium position and released. The spring constant is 5 N/m

    What is the total energy of the block-spring system?

    My book says E = K + U or E = (1/2)mv^2 + (1/2)kx^2. My book also says E_total = (1/2)kA(amplitude)^2. Which formula is correct? I've just solved for the E_total equation and I found the answer to be .75 J. Can anyone confirm this answer for me? My work is below...

    (1/2)(5)(.3^2) = .75 J

  2. jcsd
  3. Nov 19, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    How did you get .75J from that? Try again.
  4. Nov 19, 2006 #3
    i lied. .225 J

    Thanks for checking for me. I forgot to square the .3
  5. Nov 19, 2006 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    With that cleared up.

    The 2 relationships you have posted.

    [tex] E = K + U = \frac 1 2 m v^2 + \frac 1 2 k x^2 [/tex]


    [tex] E = \frac 1 2 k A^2 [/tex]

    are the same. The amplitude is defined as when the displacement is at its maximum so A = x. At the point in time when the displacement is at its maximum, the velocity is zero. So in the first relationship, let x=A and v=0.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Similar Threads for Spring Date
Energy stored in a spring Today at 1:11 AM
Resultant force of spring at the instant of release? Thursday at 8:53 PM
Spring, SHM Thursday at 12:50 PM
Spring balance question Apr 13, 2018
Damped harmonic oscillator for a mass hanging from a spring Apr 6, 2018