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!

Jumping box with a spring and mass inside

  1. May 24, 2014 #1
    1. The problem statement, all variables and given/known data
    Inside a mass M box, over a horizontal floor, there are a massless spring of elastic constant k, fixed to a body of mass m. That body is trapped to a wire in the bottom of the box. After the wire breaks the box will jump with which deformation b of the spring?
    2. Relevant equations
    F=m.g
    F=k.b
    3. The attempt at a solution
    I know the answer is that below but i just can't think how would I get to it.
    b > (M + 2m)g/k.
     

    Attached Files:

    Last edited: May 24, 2014
  2. jcsd
  3. May 25, 2014 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    Hi Zeor137. I think what happens is that in the situation shown, the spring is stretched. When the wire is cut, the mass m accelerates upwards until the spring becomes compressed by almost as much as it had been stretched (less an allowance for the weight of m).

    I haven't worked it out, so I can't be certain that that's the right way to view it.
     
  4. May 25, 2014 #3

    berkeman

    User Avatar

    Staff: Mentor

    Welcome to the PF. Please use NO's hint to help you work this problem. We do not allow posts here where you do not show your work toward a solution.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Jumping box with a spring and mass inside
Loading...