Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Example of conservative and non conservative force

  1. May 1, 2012 #1
    Hello frnds, i understand what conservative and non conservative force are but i didn't get it properly with practical example. so any article is there which explain it properly with practical example and in easy way, i searched but didn't get any article that satisfy me.
  2. jcsd
  3. May 1, 2012 #2
    Gravity is conservative, friction is non-conservative. Drop a ball from a height of 1.00 meter. Gravity actsdownward and the energy change is simply mgh, where h is height, 1.00 meter. Upon impact the ball heads upward. Gravity is conservative, the energy stored in potential gets converted to kinetic, back to potential, etc.

    But air friction is non-conservative. During the ball's downward motion, friction (air) is taking away a fraction of its KE. The ball bounces, and the restitution is less than 100%, another non-conservative action. On the way up, friction again takes a fraction of the energy away.

    This is just 1 example, there are many others. Did this help?

  4. May 1, 2012 #3
    I got somthing but not fully, if we talkd about gravitation force acting on moon due to earth then how can we justify that it is consevative force?
  5. May 2, 2012 #4
    What does "conservative" mean to you? I've always been taught that a conservative force integrated along a path between 2 points produces the same work independent of the path. Non-conservative forces are path dependent.

    The earth-moon system is indeed conservative. The net work from point a to b then back to a is zero. That is conservative. The moon follows an elliptical orbit. The energy at some specific point in said orbit remains the same. As the distance changes so does the energy. But when the moon returns to the same point it was at previously, it has exactly the same energy as previously, no change having taken place.

    With non-conservative forces, that is not the case. Take a spring-mass system. An object rests on the floor while attached to a horizontal spring. The spring is stretched and harmonic motion occurs. If the floor was frictionless, the Hooke's law spring force would move the object towards the spring eventually compressing said spring, then the object reverses direction. At any point on the floor the object has a specific potential plus kinetic energy. After several oscillations the energy at each point remains the same.

    Now add friction. As the object oscillates, it loses energy due to friction. Spring force is conservative. Friction is not. Did I help?

  6. May 3, 2012 #5
    Yes, now i got it
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook