1. Lecture 18 Circular Orbits Newton’s Law of Gravity

2. The force of gravity is directed towards the center of the earth Circular orbit

3. Orbit just above the surface of the earth

4. Move out to the moon R em =3.84 x 10 8 m What is wrong here? What did we assume that is incorrect?

5. Newton’s Law of Gravity

6. Determine the mass of the earth M 1 is your mass = ____________ R earth = 6.37 x 10 6 m G=6.67 x 1011 Nm 2 /kg 2 g=9.80 m/s 2 M 2 = Mass of the earth =

7. A typical bowling ball is spherical, weighs 16 pounds, and has a diameter of 8.5 in. Suppose two bowling balls are right next to each other in the rack. What is the gravitational force between the two—magnitude and direction? What is the magnitude and direction of the force of gravity on a 60 kg person? Example Slide 6-32

8. Slide 6-38 A coin sits on a rotating turntable. 1.At the time shown in the figure, which arrow gives the direction of the coin’s velocity?

9. A coin sits on a rotating turntable. 2.At the time shown in the figure, which arrow gives the direction of the frictional force on the coin? Slide 6-40

10. Slide 6-42 A coin sits on a rotating turntable. 3.At the instant shown, suppose the frictional force disappeared. In what direction would the coin move?

11. 6.7 Gravity and Circular Orbits M = mass of parent, m=mass of satellite Kepler’s law

12. Geostationary Satellite At the equator, how far above the earth’s surface should a satellite orbit so it stays overhead? R earth = 6.37 x 10 6 m G=6.67 x 1011 Nm 2 /kg 2 M earth = 5.98 x 10 24 kg