1. Gravitation

2. What affects the Gravitational Force between…
The Sun and Earth?
The Moon and Earth?
An apple and Earth?

3. Since we can’t measure these forces, we will infer them…
A net force causes…

4. Since we can’t measure these forces, we will infer them…
A net force causes acceleration The gravitational force acting on an orbiting satellite is (basically) the net force on it. This force points…

5. Since we can’t measure these forces, we will infer them…
A net force causes acceleration The gravitational force acting on an orbiting satellite is (basically) the net force on it. This force on the satellite points toward the center of the orbit. The satellite’s ______________ is proportional to the size of this force.

6. Since we can’t measure these forces, we will infer them…
A net force causes acceleration The gravitational force acting on an orbiting satellite is (basically) the net force on it. This force on the satellite points toward the center of the orbit. The satellite’s centripetal acceleration is proportional to the size of this force. What is the mathematical relationship between a planet’s ______________ and its ____________________?

7. Since we can’t measure these forces, we will infer them…
A net force causes acceleration The gravitational force acting on an orbiting satellite is (basically) the net force on it. This force on the satellite points toward the center of the orbit. The satellite’s centripetal acceleration is proportional to the size of this force. What is the mathematical relationship between a planet’s centripetal acceleration (mm/s/s) and its distance from sun (106km) ?

8. Lab:
What is the mathematical relationship between a planet’s centripetal acceleration (mm/s/s) and the radius of its orbit (106km OR Gm OR 109m) ?

9. For Planets orbiting the sun (and anything orbiting anything)…
Centripetal acceleration is inversely proportional to distance from center of orbit squared. Orbiting twice as far away results in one fourth as much centripetal acceleration. Three times as far away, one ___________ as much…

10. Putting M, m together with r…

11. Newton’s Law of (universal) Gravitation
Fg = G m1 m2 / r2 Fg = G (M × m) / r2

12. The Cavendish Apparatus

13. Principal of Superposition
Sounds hard, but it means the net force on object #1 due to objects 2, 3, 4, …, is merely the vector sum of the force 2 exerts on 1, plus the force 3 exerts on 1 plus….

14. Example Problems: Determine the force between…
The Sun and Earth
The Moon and Earth

15. More Examples: Compute g on the surface of…
the Moon Jupiter Mars Earth

16. One More Example…
The International Space Station orbits Earth once every 92 minutes. Compute its ALTITUDE.