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: Mechanical Energy

  1. Mar 9, 2007 #1
    1. The problem statement, all variables and given/known data

    Zero, a hypothetical planet, has a mass of 1.0x10^23 kg, a radius of 3.0x10^6 m, and no atmosphere. A 10 kg space probe is to be launched vertically from its surface.
    (a) If the probe is launched with an initial kinetic energy of 5.0x10^7 J, what will be its kinetic energy when it is 4.0x10^6 m from the center of Zero?

    2. Relevant equations

    (1/2)mv^2 - (GMm/R)=(1/2)mv^2 - (GMm)/(10R)

    3. The attempt at a solution

    5.0e7 - [(6.67e-11)(1e23)(10)]/(3e6)= KE - [(6.67e-11)(1e23)(10)]/(10(4e6)]

    I don't think that I am using the right values for R though. Am I???
  2. jcsd
  3. Mar 9, 2007 #2


    User Avatar
    Gold Member

    I can't see where the 10R comes from. Should be R as on the LHS.
  4. Mar 9, 2007 #3
    ok, well do I have the correct values of R set up in the equation or do I need to take the difference of the distance of the satellite to the center or anything?
  5. Mar 10, 2007 #4


    User Avatar
    Gold Member

    I think all your distances are measured from the centre of Zero.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook