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!

Newton's Theory of Gravity

  1. Oct 22, 2006 #1
    A 1.0 kg object is released from rest 500 km above the earth.
    A. What is its impact speed as it hits the ground? Ignore air resistance
    B. What would the impact speed be if the earth were flat?
    I don't know how to start this.
    I said that v=sqrt(2G*M_e*m/(R_e+300))= 1.33*10^9 but that is incorrect....I'm probably being stupid but please help
  2. jcsd
  3. Oct 22, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper

    You seem to recognize that this problem has something to do with energy conservation. With the reference of zero potential at infinity the object has potential energy at altitude, but also when it hits the ground. You have several dimensional inconsistencies in your equation. What is 300? Why are there both M_e and m on the right and no m on the left.?

    I have no idea what part C is about. Flat how? A cube? A huge plane of mass? I have no idea.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Newton's Theory of Gravity
  1. Newton theory of gravity (Replies: 27)