**♦ You should be able to rewrite these laws in your own words and demonstrate understanding of these laws both in our own SOLar System and in other stellar systems in our galaxy ( ***the following text comes from our good friends at Georgia State University hyperphsics.com***)**:

1. Law of Orbits: All planets move in elliptical orbits, with the sun at one focus.

2. The Law of Areas: A line that connects a planet to the sun sweeps out equal areas in equal times.

3. The Law of Periods: The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit. You should be able to recognize when to use each of the following variations of Kepler's 3rd as well as explain the differences in the following versions of the *The Law of Periods*:

T^{2} = A^{3}

General (*and easiest*) form for use for objects orbiting the sun in our solar system. T is measured in years and A is measured in *AU*s

T^{2} = M_{s}A^{3}

General form for use for objects orbiting other stars in other stellar systems. T is measured in years, A is measured in *AU*s and *M*_{s} is in decimal parts of our sun's mass.

T^{2} = (4π^{2} /GM_{s})A^{3}

NASTY form for use for objects orbiting the sun in SIUs: T is measured in seconds, A is measured in *meters* and *M*_{s} is the mass of the sun in kgs

**♦ Utilize and explain the physics represented by the formulas for centripetal acceleration**:

A_{c} = v^{2}/r

**♦ Utilize and explain the physics represented by the formulas for centripetal force**:

f_{c} = mv^{2}/r

**♦ Utilize Newton's Law of Gravitation**:

F_{g} = Gm_{1}m_{2}/r^{2}

**♦ Compare and combine ***gravitational force* to *centripedal force*:

Gm_{1}m_{2}/r^{2} = mv^{2/}r