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!

Classical mechanics - Energy balance confussion

  1. Jul 9, 2015 #1
    Hi everyone.
    I'm confused with the balance of energy in this situation (I'm comparing the mechanical energy, initially, at rest, at a height = h, and then, at the end, at height = 0). It doesn't seem to be fine, maybe I missed something.
    I'd appreciate some help - Everything is in the .jpg below.

    There are 2 relevant equations:
    1. The work done by a nonconservative force is equal to the change in mechanical energy. (Wnc = Delta E)
    2. W = Force (dot) distance.
    Also, take into account that h / sin(theta) is equal to the hypotenuse of the inclined plane.
     

    Attached Files:

    Last edited: Jul 9, 2015
  2. jcsd
  3. Jul 9, 2015 #2

    Doc Al

    User Avatar

    Staff: Mentor

    It's a bit difficult to follow. And since you put your work in a jpg instead of typing it here, it is hard to comment.

    One thing: You seem to mix up the height h with the distance along the surface.
    And another: You may have mixed up some signs.
     
  4. Jul 9, 2015 #3
    Hmmm, right. y(t) gives me the displacement along the surface (not the height).
    Give me some minutes and I'll have the equations fixed.

    * EDIT: Doc Al, you were right. I rewrote the equations by hand and everything fits well now, thanks.
    I just had to change the limits in one integral at the beginning of the deductions.
     
    Last edited: Jul 9, 2015
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Classical mechanics - Energy balance confussion
  1. Classical Mechanics (Replies: 4)

  2. Classical Mechanics (Replies: 4)

Loading...