1. What can you tell me about gravity?

2. Gravity is usually assumed to be a uniform vertical downward force......it is actually radial

3. g = 9.81ms -2 is not constant! Watch video clip

4. Do now: copy the notes, answer the questions, and... May the Force (of Gravity) Be With You! 1)G = 6.67 x 10 -11 - what are the units? 2)Calculate the force of gravitational attraction between you and another person in the room. 3)How does this compare to your weight force? Newton’s Law of Gravitation: Nm 2 /kg 2 (their centres) Board notes!

5. 1)G = 6.67 x 10 -11 - what are the units? 2)Calculate the force of gravitational attraction between you and another person in the room. 3)How does this compare to your weight force? Newton’s Law of Gravitation: Nm 2 /kg 2 (their centres)

6. Learning Outcome : Use Newtons Law of Gravitation to calculate gravitational force and satellite speed Geostationary satellites: T = 24 hours Satellite velocity does not depend on its mass - so all geostationary satellites orbit at the same radius!

7. Geostationary orbit : radius = 35,786 km, velocity = 3.07 km/s

8. A 110kg satellite is placed in orbit around the Earth at a height of 35,900km. Use m E = 5.98 x 10 24 kg and r E = 6370km to calculate: a)The force of gravity on the satellite b)The orbital speed c)The orbital period (in hours) a) 25N b) 3100ms -1 c) 24 hours Example: Trivia: how many satellites are there in space? 24,500 (Space Surveillance Network actively tracks 8,000 of these, 560 of which are currently operational). The Global Positioning System (GPS) is a US-owned global navigation satellite system that makes use of 24 to 32 satellites.

9. Video clips Activity 8C