1. Physics Section 7.3 Apply Kepler’s Laws of Planetary Motion The Polish astronomer Nicolas Copernicus was the first to correctly place the sun at the center of our solar system. 1 st Law: Each planet travels in an elliptical orbit around the sun and the sun is at one of the focal points Johannes Kepler perfected the Copernicus model by devising three laws of planetary motion.

2. 2 nd Law: An imaginary line drawn from the sun to the planet sweeps out equal areas in equal times.

3. 3 rd Law: The square of the planet’s orbital period (one year) is proportional to the cube of the average distance between the planet and the sun. T = period (s) m = mass of star(object being orbited) (kg) r = average distance from planet to sun G = 6.67 x 10 -11 N m 2 /kg 2 T 2 = or T = and v t = Gm r

4. example A large planet orbiting a distant star is discovered. The planet’s orbital distance is 7.5 x 10 10 m, and its period is 105.5 days. Calculate the mass of the star and the planets orbital speed.

5. example A satellite is to orbit above the Earth at an altitude of 350 km. Find the velocity required to maintain a circular orbit. What is the period of the orbit?

6. assignment page 253 Problems 1,2,5,6,7