• ### Gravitational potential energy

Is defined by the integral:

 U(r) = -  Where is the force due to gravity and we define U(∞) = 0. Doing the integral gives:

 U(r) = - which reduces to U = mgh near the earth.

• ### Gravitational potential

Is defined as the gravitational potential energy that a 1 kilogram mass would have at some point in space. It is given by:

 Φg = - which reduces to Φg = gh near the earth.

• ### Principle of Equivalence

Asserts that all types of matter fall at the same rate. That is, g for a brick is the same as g for water. This means that the inertial mass appearing in Newton's Second Law is equivalent to the gravitational mass appearing in the Universal Law of Gravitation.

• ### Inertial mass

The mass mi that appears in Newton's Second LawF = mia.

• ### Gravitational mass

The mass that appears in the Universal Law of Gravitation.

• ### Shell Theorem

States that any spherical mass can be treated as though all its mass were concentrated at its center for the purposes of calculating gravitational force. Also, that a spherical shell of matter exerts no gravitational force on a mass inside it.

• ### Formulae

Energy for a circular orbit around the sun

 E = 