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: Throw a ball up how high does it go

  1. Apr 3, 2008 #1
    An object is projected straight upward from the surface of Earth with an initial speed of 2.98 km/s. What is the maximum height it reaches?

    Ok i know this seams like a really easy problem but i cant figure it out... since this question is from our chapter on gravity i have trued usuing is ke initial = potential energy final...
    ke initial being(1/2 m v^2) and potential energy final being: (GMm/r^2)^1/2 M is the mass of the earth and m is the mass of the ball
  2. jcsd
  3. Apr 3, 2008 #2
    You're not going to throw the ball so high that its distance to the center of mass of the earth will change by a significant percentage. g is nearly constant. Therefore PE at height h will be mgh.
  4. Apr 3, 2008 #3
    he said 2.98 km/s. that will get you high enough for g get significantly smaller.

    the potential energy for a mass at distance r from the earth is -GmM/r, if the potential at infinity is 0, so there is both an initial and a final potential energy.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook