Chapter 12: Gravity Reference Tools & Resources

Reference Tools & Resources

I. Key Terms and Phrases

gravity: one of the fundamental forces of nature that represents the attraction between two objects with mass.

Newton's law of universal gravitation: between any two point masses there is an attractive force directly proportional to the product of the masses and inversely proportional to the square of the distance between them.

principle of superposition (for gravity): the net result of the gravitational interaction within a system of many particles is the sum of the results for interactions between each pair of particles in the system.

orbital period: the amount of time it takes an object to execute one complete orbit.

escape speed: the speed at which a moving object can just barely escape the gravitational pull of another object by having the ability to get infinitely far away. At this speed the mechanical energy of the system is zero.

II. Important Equations

Name/Topic	Equation	Explanation
gravitational force		The magnitude of the gravitational force between two masses.
gravitational acceleration		The acceleration due to gravity near the Earth's surface.
circular orbits		The equation form of Kepler's third law for the case of a circular orbit.
potential energy		The gravitational potential energy of two point masses.
escape speed		The escape speed of an object a distance r from an object of mass M.

III. Know Your Units

Quantity	Dimension	SI Unit
universal gravitational constant (G)

Reference Tools and Resources by David Reid, Eastern Michigan University. ©2002 by Prentice Hall, Inc.

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