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Orbits and Gravity

Orbits and Gravity . Kepler’s Laws Newton’s Laws Gravity, Mass, and Weight. Empirical Law. A simple relationship or formula that is found through observations or experiment, and does not address the reason WHY it happens. Opposite: Theory. Galileo Galilei Italy 1564-1642.

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Orbits and Gravity

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  1. Orbits and Gravity • Kepler’s Laws • Newton’s Laws • Gravity, Mass, and Weight

  2. Empirical Law • A simple relationship or formula that is found through observations or experiment, and does not address the reason WHY it happens. • Opposite: Theory

  3. Galileo GalileiItaly 1564-1642

  4. Tycho BraheGermany1546-1601 http://en.wikipedia.org/wiki/Image:Tycho_Brahe.JPG

  5. Johannes KeplerGermany1571-1630 http://en.wikipedia.org/wiki/Image:Johannes_Kepler_1610.jpg

  6. Kepler’s Laws • Ellipses • Equal Areas • P2=a3

  7. 1. Planets orbit the Sun in ellipses, with the Sun at one focus

  8. http://www.astro.virginia.edu/class/oconnell/astr121/im/ellipse-geom-NS.gifhttp://www.astro.virginia.edu/class/oconnell/astr121/im/ellipse-geom-NS.gif

  9. http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/kep5.gif

  10. Kepler’s Laws • Ellipses • Equal Areas • P2=a3

  11. 2. Planets’ orbits sweep out equal areas in equal times.

  12. http://physics.uwyo.edu/~stark/outreach/Kepler/oldareaellipse.gifhttp://physics.uwyo.edu/~stark/outreach/Kepler/oldareaellipse.gif

  13. http://upload.wikimedia.org/wikipedia/commons/7/75/Kepler2.gifhttp://upload.wikimedia.org/wikipedia/commons/7/75/Kepler2.gif

  14. 2. Planets’ orbits sweep out equal areas in equal times. When one planet is closer to the Sun, it moves faster than when it is farther from the Sun.

  15. Kepler’s Laws • Ellipses • Equal Areas • P2=a3

  16. 3. P2=a3 • Period - in Earth years • Semi-major axis (average distance from the Sun) - in AU • Planets closer to the Sun orbit in a shorter time.

  17. P^2=a^3

  18. Planets

  19. 3. P2=a3 • Period - in Earth years • Semi-major axis (average distance from the Sun) - in AU • Planets closer to the Sun orbit in a shorter time.

  20. Kepler’s Laws • Ellipses • Equal Areas • P2=a3

  21. Sir Isaac NewtonEngland1643-1727 http://en.wikipedia.org/wiki/Image:GodfreyKneller-IsaacNewton-1689.jpg

  22. Newton’s Laws • Inertia • F=ma (Forces) • Action and reaction

  23. 1. Inertia • “An object in motion tends to stay in motion, and an object at rest tends to stay at rest, unless acted upon by an outside force.” • The Couch-Potato Law: Things keep doing the same thing.

  24. 2. F=ma (Forces) • “When a force (F) acts on a body, it produces an acceleration (a) equal to the force divided by the mass (m).” • It takes more force to change the motion of heavier objects.

  25. 3. Action and Reaction • “For every action there is an equal and opposite reaction.” • Every time one object causes a force on another, the first object experiences the same force. • They will not experience the same acceleration because their masses are different.

  26. Gravity Force that pulls all objects with mass towards all other objects with mass. F=GMm/r2 Newton’s Laws plus Gravity explain all of Kepler’s Laws.

  27. Kepler’s Laws and Newton Ellipses Gravity (F=GMm/r2) makes objects move in this sort of shape. Equal Areas Conservation of Angular Momentum, which follows from Newton’s Laws. P2=a3 Gravity (F=GMm/r2) causes this too.

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