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!

Work and spring

  1. Oct 17, 2012 #1
    does spring always do negative work?

    how could it do positive work?

    I can't think of any situation
  2. jcsd
  3. Oct 17, 2012 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member


    Suppose you have a spring with a mass at the end of it. The spring is compressed, because you are pushing on the mass and holding it there. Then you release it. The restoring force acts to extend the spring, pushing the mass outward along with it. The displacement of the mass is in the same direction as the force. Therefore, the force does positive work. You *know* that it has done positive work, because the kinetic energy of the mass has increased.

    It's only once the spring extension goes past the equilibrium position, and the spring becomes stretched, that the restoring force switches sign and starts to pull the thing back.
  4. Oct 17, 2012 #3
    Thank you so much :D
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook