1. Universal Gravitation Aim: How does the mass of an object affect gravitation?

2. Gravitational Field Lines All masses produce a gravitational field that points straight towards its center

3. When two or more masses are close together, their gravitational fields combine and the objects feel the SAME gravitational force

4. Universal Gravitation All masses in the universe ATTRACT one another with a mutual force that is proportional to their mass but inversely proportional to the square of their distance Force of Gravity Units: Newtons (N) Masses Units: Kilograms (kg) Distance between object’s centers -OR- Radius Units: meters (m)

6. Example #1 Determine the gravitational force between the Earth and the Moon r = 3.84×10 8 m m Earth = 5.98×10 24 kg m moon = 7.35×10 22 kg

7. Example #2 A 1,630kg GPS satellite has a radial orbit of approximately 27Mm from the center of the earth. How fast must the satellite travel in order to maintain its geosynchronous orbit?

8. Example #2 A 1,630kg GPS satellite has a radial orbit of approximately 27Mm from the center of the earth. How fast must the satellite travel in order to maintain its geosynchronous orbit?

9. What Happens to Your Body in Space without a Space Suit? Swell Up – Lack of atmosphere Burn – UV Rays Mutate – Gamma Rays Pass Out – Lack of Oxygen Rupture Lungs – Lack of Pressure

10. Ratio Method When dealing with problems that typically ask what will happen when you DOUBLE/TRIPLE/HALVE/ETC. a variable, follow these steps: Using the equation as a model, plug in ONES for all variables IGNORE ANY CONSTANTS Solve the equation and see what you get Then plug in the variables according to what the PROBLEM SAYS while leaving all other variables as ones Compare the two answers

11. Examples How does the force of gravity change if BOTH masses double? The force QUADRUPLES!

12. Examples How does the force of gravity change if the distance doubles? The force QUARTERS!

13. Examples How does the force of gravity change when… One mass is doubled? Both masses are tripled? One mass is doubled while the other is halved?

14. Examples How does the force of gravity change when the distance… Triples? Is halved? Is quartered

15. SUMMARY How do you calculate the force of gravity between two objects? What does G represent and what is its value? How does the force of gravity change when… – Mass changes? – Distance changes?