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Weight and gravitational force?

  1. May 26, 2013 #1
    Hi, I'm wondering if anybody could explain me the difference between these two concepts with a clear definition for someone who JUST began physics. Thanks ! Particularly, concerning this equation w=Fg=mg

    Also, just to be sure I'm doing it in the right way, could I say that would be good

    Ex : 15N=Fg=m*9,80N/Kg

    re arrange like Fg=15N=m*9,80N/Kg

    Would this be acceptable to solve for mass, knowing that these equations are equivalent ?
    Last edited: May 26, 2013
  2. jcsd
  3. May 26, 2013 #2


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    Science Advisor

    Just make sure you have the right unit for mass. It looks like kg. in your description.
    Weight is usually defined as the gravitational force on the surface of the earth.
  4. May 26, 2013 #3
    Well, it's kg, isn't that the right unit ? And for weight and Fg of an object, it's exactly the same thing ?

    If I have X N of weight, it means the gravitational force which gives that weight to the object will have the same numerical value ?

    is this a good way of viewing it ? thanks
  5. May 26, 2013 #4

    Doc Al

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    Staff: Mentor

    Yes, kg is the standard SI unit for mass.

    No. Weight is a force; the standard SI unit for force is the Newton.

    No. Near the earth's surface, a 1 kg mass will have a weight of W = mg ≈ (1 kg)*(9.8 N/kg) = 9.8 N.
  6. May 26, 2013 #5
    Sorry if I misleaded you, I didn't mean that weight and Fg was in Kg. xD

    It's just I don't see the relationship between weight and Gravitational force of an object.

    Does w=mg and Fg=mg mean the same exact thing ??? Could you tell it to me ??? thanks again
  7. May 26, 2013 #6

    Doc Al

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    Staff: Mentor

    They are the same thing: the weight of an object is the gravitational force exerted on it by the earth.

  8. May 26, 2013 #7
    Ahhhhhhhhhhhhhhhhhh... Finally, that's what I wanted to read and be confirmed. Now, that makes me happy ! Thanks you and everyone else who posted !
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