l5p - Today Announcements HW#3 is due by 8:00 am Wednesday...

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ISP209s8 Lecture 5 -1- Today • Announcements: – HW#3 is due by 8:00 am Wednesday January 30th. – A second extra credit problem will be available next week • Gravity • Force • Vectors ISP209s8 Lecture 5 -2- History of astronomy Ptolomy devised an Earth-centered model of the motion of planets that worked well Brahe made detailed measurements that showed deficiencies in the model Kepler discarded the previous assumptions and devised his three laws of planetary motion with the Sun at the center Newton unified the tree laws with his Universal Law of Gravity ISP209s8 Lecture 5 -3- Planetary Orbits We will use the program Interactive Physics to demonstrate planetary orbits. Newton recognized the acceleration of the Moon and knew that a force from the Earth must be responsible. He called this gravity. At the time it was questioned because people would not accept force at a distance. But, what does cause gravity? More later … ISP209s8 Lecture 5 -4- Newton’s Universal Law of Gravity Newton’s Universal Law of Gravity: 2 2 2 2 1 11 673 . 6 ; kg Nm E G r m Gm F = = WHY?
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