# l5 - Today Announcements HW#3 is due by 8:00 am Wednesday...

This preview shows pages 1–6. Sign up to view the full content.

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 •F o r c e • Vectors

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
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 …

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
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?
ISP209s8 Lecture 5 -5- The Law of Gravity What is the force of gravity on a 90 kg professor standing on the surface of the Earth? () N m E kg E kg kg Nm E r m Gm F e e p 882 6 378 . 6 24 974 . 5 90 11 673 . 6 2 2 2 2 = × = = Note: We get the same answer if we ask what is the force a professor exerts on the Earth. That is Newton’s third law.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 20

l5 - Today Announcements HW#3 is due by 8:00 am Wednesday...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online