# ap-physics-c-exam-review-4.doc - AP Physics C Mechanics...

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AP Physics C Mechanics Review Sheet #4 -Newton’s Law of Universal Gravitation The gravitational force between two objects is directly related to the product of the masses of the objects and inversely related to the distance between their center of masses squared 2 G GMm F r When an object is located inside the surface of the larger object, only the mass beneath the object being affected applies a force. One must use the assumption that the planet is of uniform density, so that the large M in the equation is replaced by 3 4 3 M r , where rho is the density. The force of gravity equation is then: 4 3 G F r Gm   -Gravitational Potential Energy At infinity, the gravitational potential energy that an object experiences is zero, and as it gets closer to the source, the potential energy must decrease. So, the gravitational potential energy should be negative G GMm U r   -Circular Orbits For objects traveling in circular orbits, e.g., satellites, one should set the force of gravity equal to the