1. Phys 150 Lecture 71 Please sit together in pairs: –Onyema and Michael –Alejandra and Honglu –Chris and Matt –Ryan and Lin –John F. and Anwen –Walter and Mengyue –Max and Melissa –Amanda and Zhongyun –Pauline and Kaijun –Jake and Erich –John W. and Irfan –Jennifer and Jason –Alexandra and Jiayuan –David and Erica –Abigael and Dian

2. Phys 150 Lecture 72 Announcements Homework 4 is due on Sunday at midnight. Please check your quiz, homework (and reports), and i>clicker scores on the Gradebook. Email me if there are any problems. James Scholar honors project: email me

3. Phys 150 Lecture 73 Announcements Guidelines for essays are posted on the course web page. Your essay should –Answer the question –Contain reasoned arguments –Contain relevant facts/numbers from the book/lecture –Consider a broad range of solutions –Have correct spelling and grammar

4. Phys 150 Lecture 74 Chapter 3 – Gravity, Force, Space On the surface of the Earth, everything falls with acceleration g=10 (m/s)/s Feather and coin

5. Phys 150 Lecture 75 Chapter 3 – Gravity, Force, Space On the surface of the Earth, everything falls with acceleration g=10 (m/s)/s Feather and coin Apollo 15 1971

6. Phys 150 Lecture 76 i>clicker question The acceleration due to gravity on the moon (g moon ) is about A.2g B.g/2 C.g/6 D.g/200

7. Phys 150 Lecture 77 i>clicker question The acceleration due to gravity on the moon (g moon ) is about A.2g B.g/2 C.g/6 D.g/200

8. Phys 150 Lecture 78 i>clicker question An astronaut is floating inside a spaceship that is drifting through space. The spaceship begins to fall, nose first, toward a planet. The astronaut A.is pushed toward the front of the ship B.is pushed toward the rear of the ship C.continues to float inside the ship

9. Phys 150 Lecture 79 i>clicker question An astronaut is floating inside a spaceship that is drifting through space. The spaceship begins to fall, nose first, toward a planet. The astronaut A.is pushed toward the front of the ship B.is pushed toward the rear of the ship C.continues to float inside the ship

10. Phys 150 Lecture 710 i>clicker question A satellite in low Earth orbit (LEO) is travelling at about A.50 miles/hour B.5 miles/sec C.500 meters/sec D.It depends a lot on its altitude

11. Phys 150 Lecture 711 i>clicker question A satellite in low Earth orbit (LEO) is travelling at about A.50 miles/hour B.5 miles/sec C.500 meters/sec D.It depends a lot on its altitude -5 miles/sec at an altitude around 100 miles -Earth radius is 4000 miles - Spy satellites can only view a given area for about a minute

12. Phys 150 Lecture 712 Spy satellite photo

13. Phys 150 Lecture 713 International Space Station

14. Phys 150 Lecture 714 Landsat GRACE

15. Phys 150 Lecture 715 i>clicker question A satellite in geosynchronous orbit is about how far above the surface of the Earth? A.1200 miles B.12,000 miles C.22,000 miles D.120,000 miles

16. Phys 150 Lecture 716 i>clicker question A satellite in geosynchronous orbit is about how far above the surface of the Earth? A.1200 miles B.12,000 miles C.22,000 miles D.120,000 miles -22,000 miles is more than 5 Earth radii - geosynchronous orbit is above the equator

17. Phys 150 Lecture 717 Geosynchronous weather satellite Also great for communication satellites

18. Phys 150 Lecture 718 Space debris

19. Phys 150 Lecture 719 i>clicker question There are relatively few satellites in medium earth orbit (MEO) because A.they are not geosynchronous B.they are too high to make good spy satellites C.they are mostly GPS satellites D.All of the above

20. Phys 150 Lecture 720 i>clicker question There are relatively few satellites in medium earth orbit (MEO) because A.they are not geosynchronous B.they are too high to make good spy satellites C.they are mostly GPS satellites D.All of the above - GPS = Global Positioning System uses about 24 MEO satellites at an altitude of 12,000 miles. They orbit the Earth every 12 hours.

21. Phys 150 Lecture 721 GPS

22. Phys 150 Lecture 722 i>clicker question To escape completely from the Earth, a rocket must attain a minimum velocity of A.5 miles/sec B.7 miles/sec C.20 miles/sec D.32 miles/sec

23. Phys 150 Lecture 723 i>clicker question To escape completely from the Earth, a rocket must attain a minimum velocity of A.5 miles/sec B.7 miles/sec C.20 miles/sec D.32 miles/sec -5 miles/sec is LEO -7 miles/sec is escape velocity - 20 miles/sec is the velocity of the Earth around the sun

24. Phys 150 Lecture 724 i>clicker question A car travelling 60 mph collides with a bus travelling 20 mph. The force of the car on the bus is A.Less than the force of the bus on the car B.Greater than the force of the bus on the car C.Equal to the force of the bus on the car D.It depends on whether the collision is head-on or from the rear

25. Phys 150 Lecture 725 i>clicker question A car travelling 60 mph collides with a bus travelling 20 mph. The force of the car on the bus is A.Less than the force of the bus on the car B.Greater than the force of the bus on the car C.Equal to the force of the bus on the car D.It depends on whether the collision is head-on or from the rear

26. Phys 150 Lecture 726 Newton’s Third Law Forces always come in pairs –Every “action” has an equal and opposite “reaction” Skateboard Balloon