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!

Maximum acceleration of a spring

  1. Apr 12, 2016 #1
    1. The problem statement, all variables and given/known data
    A spring with a spring constant of 5.0 N/m has a 0.25 kg box attached to one end such that the box is hanging down from the string at rest. The box is then pulled down another 14 cm from its rest position. Calculate the maximum height, the maximum speed, and the maximum acceleration of the box.
    2. Relevant equations


    3. The attempt at a solution
    I found maximum speed and height but I cant find the maximum acceleration
    ma= kx+mg
    (o.25)a= (5)(0.14m)+(0.25)(9.81)
    a=12.61 m's^2
    the answer is 2.8m/s^2
    what am I doing wrong?
     
  2. jcsd
  3. Apr 12, 2016 #2

    gneill

    User Avatar

    Staff: Mentor

    Draw the FBD.

    When the spring is stretched "another 14 cm", what is the total displacement of the spring? So what force does it apply? What direction?
     
  4. Apr 12, 2016 #3
    is it ma=kx-mg instead of ma=kx+mg, even then I don't understand how acceleration can equal to 2.8m/s^2
     
  5. Apr 12, 2016 #4

    gneill

    User Avatar

    Staff: Mentor

    You didn't answer my question: When the spring is stretched "another 14 cm", what is the total displacement of the spring? What was the initial displacement when the mass was just hanging at rest on the end of the spring?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted