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Weight of object below the Earth's surface.

  1. Oct 18, 2014 #1
    1. The problem statement, all variables and given/known data

    Calculate the gravitational force acting on a 9.6-kg mass....?
    1.5 x 10^4 m above Earth's center. How do i solve this??
    2. Relevant equations


    3. The attempt at a solution
    the answer is 17N but i dont understand how
     
  2. jcsd
  3. Oct 18, 2014 #2

    NascentOxygen

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    Staff: Mentor

    Hi rrosa522. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    What is the equation for gravitational force between m1 and m2 spaced a distance r apart? If not in your text book, use google.
     
    Last edited by a moderator: May 7, 2017
  4. Oct 18, 2014 #3

    SteamKing

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    This chap Isaac Newton had stuff like this figured out.
     
  5. Oct 18, 2014 #4
    i must admit that after reading this threads title i was disappointed by its content XD
     
  6. Oct 18, 2014 #5
    try and use this equation:
    [itex] F_{grav} = \frac{Gm_{1}m_{2}}{r^2} [/itex]
    Where m1 and m2 are two masses, r is a distance and G is a constant
     
  7. Oct 18, 2014 #6
    i tried the formula but i dont get 17N
     
  8. Oct 18, 2014 #7
    you should have the mass of earth (its probably in your textbook) we can call this m1, the other mass is given to you. You have the distance of the object, so enter these values into the formula given above
     
    Last edited: Oct 18, 2014
  9. Oct 18, 2014 #8
    Better yet, show me what you are entering in the formula
     
  10. Oct 18, 2014 #9

    gneill

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    A distance of 1.5 x 10^4 m from the Earth's center is well below the Earth's surface, and within the inner core. How did you apply Newton's gravitational force law for that location? Show your work.

    Where did your answer of 17N come from ?

    Also, your thread title does not meet Physics Forums requirements; thread titles should be descriptive of the thread content, describing the problem or area of physics involved. Please note this for future questions that you post. I have changed the title to be more appropriate.
     
  11. Oct 18, 2014 #10
    I'm sorry, I read the problem as 1.5x10^4 from the earth's surface....either way show how you are using the formula
     
  12. Oct 18, 2014 #11
    (6.67x10^-11) (9.6) (5.97 x 10^24) /
    (1.5 x 10^4)^2
    the answer i get 1.70x10^7 N
    (sorry i didnt add units in my solution, its just gets confusing for me)
    the answer at the the back of my textbook is 17 N, i don't understand why
     
  13. Oct 18, 2014 #12
    (6.67x10^-11) (9.6) (5.97 x 10^24) /
    (1.5 x 10^4)^2
    the answer i get 1.70x10^7 N
    the answer at the the back of my textbook is 17 N, i don't understand why
     
  14. Oct 18, 2014 #13

    gneill

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    Staff: Mentor

    The textbook is wrong if the radius that you specified is correct.

    17 N would be correct if the given radius was in km not meters. That would place the 9.6 kg object well above the Earth's surface. Check the units on the given radius.
     
  15. Oct 19, 2014 #14
    let take one object as earth and other as the object
    there distance as 1.5 x 10^4
    f=gM1m2/d^2
     
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