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!

Homework Help: Obtaining kinetic energy equation.

  1. Apr 2, 2015 #1
    The question is about 2 sticks standing above eachother, but i have a more general question.

    The position of my mass is described by: (2rsin(a) - rsin(b) , 2rcos(a)+rcos(b))

    the goal is to get a formula for the kinetic energy, so i need the speed of the mass.

    If i take the derivatives of both functions i get the speed in x and y direction.

    So my question is: is it allowed for the v in (mv^2)/2 to summ up the velocities in both directions and to use it as the formula of v in the kinetic energy equation

    This is my first post on this forum, so sorry for the lay-out of this question which is probably wrong...
    Last edited by a moderator: May 17, 2015
  2. jcsd
  3. Apr 2, 2015 #2
    Welcome to PF!

    You can't just sum them, you have to use Pythagoras' theorem.
  4. Apr 2, 2015 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    From which it follows that what you can do is calculate the KEs in the two directions separately and add those.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted