1. Not finding help here? Sign up for a free 30min 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!

Energy ratio?

  1. Oct 14, 2008 #1
    What is the energy ratio (Ef/Ei) of a system on Earth that has a final velocity of 3901.5 cm/s, initial velocity of 249.9 m/s, and a height of 0.006 km.

    E = K + U
    = 1/2mv^2 + mgh

    Ef = 1/2mvf^2 + mghf
    Ei = 1/2mvi^2 + mghi

    It appears that the object is being forced upwards since the vi>vf. I tried several times setting hi = 0 and hf = 6m, but I can't seem to come up with the correct answer.
  2. jcsd
  3. Oct 14, 2008 #2
    You do want the energy ratio... did you find Ef and Ei and then divide? Also -- I notice here that vf seems to have units of cm/s... is that right and did you take that into account?... might just be these bookkeeping things.
  4. Oct 14, 2008 #3
    Yes, I'm trying to solve the energy ratio. I did take into account that vf has units of cm/s. Under normal circumstances, hf = 0, and vf>vi. I made the assumption, based on the values given, that hi = 0, and that an upward force is being applied.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Energy ratio?
  1. Kinetic Energy Ratios (Replies: 2)