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The Force of Gravity Depends on Two Masses

  1. Jun 30, 2014 #1
    Hello. I don't have a specific homework problem but more of an ideology problem with my brain. According to Newton's law of gravitation (written below), the force of gravity is directly proportional to the masses of both the objects under consideration. Why, then, is the force on a cart that I'm pushing solely dependent on its mass and not mine?

    Newton's Law of Universal Gravitation: F = [Gm1m]/r^2

    I have some sort of idea for an answer to this question, but none that I am able to verbalize; it's more of an intuition. Can someone much more talented than I please explain this to me in words?

    Thank you for any and all help that I receive!
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jun 30, 2014 #2


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    Homework Helper

    First, one small correction: The force is proportional to the product of the masses.

    It's just because when you push on a cart the force you're applying is not a gravitational force (and so doesn't follow Newton's law of gravity).

    Also, the force on the cart is NOT dependent on the mass of the cart. (The acceleration of the cart, however, IS dependent on the mass of the cart.)
  4. Jun 30, 2014 #3
    As (your post suggests that) you are talking about Gravitational force, then your assumption that "the force on a cart I'm pushing solely dependent on its mass and not mine" is wrong. The gravitational force between the cart and you depends on both the masses of you and the cart.
    Last edited: Jun 30, 2014
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