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: Gravitation between 4 bodies

  1. Feb 24, 2010 #1
    1. The problem statement, all variables and given/known data
    Three uniform spheres are fixed at the positions shown in the figure below. (m1 = 1.0 kg, m2 = 2.0 kg, and d = 0.60 m.)

    (See attached picture)

    (a) What are the magnitude and direction of the force on a 0.0250-kg particle placed at P?


    (b)If the spheres are in deep outer space and a 0.0250-kg particle is released from rest 300 m from the origin along a line 45° below the -x-axis, what will the particle's speed be when it reaches the origin?


    2. Relevant equations

    I used some good old trig and GMm/r^2 to get the answers to a, which were 1.11875e-11 N and 45 degrees.

    for b I really have no idea where to go with it...



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Feb 24, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: What's conserved?
     
  4. Feb 24, 2010 #3
    hmm...
    Do I need to break the problem into vector forces with GMm/r from p to each mass and find the total force by adding those?
     
  5. Feb 25, 2010 #4

    Doc Al

    User Avatar

    Staff: Mentor

    For b you need to find the speed of the particle after it moves from its initial position (how far is that position from each mass?) to its final position at point P. Hint: Calculate the change in gravitational potential energy as it moves.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook