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Universe Eighth Edition Universe Roger A. Freedman William J. Kaufmann III CHAPTER 4 Gravitation and the Waltz of the Planets CHAPTER 4 Gravitation and.

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Presentation on theme: "Universe Eighth Edition Universe Roger A. Freedman William J. Kaufmann III CHAPTER 4 Gravitation and the Waltz of the Planets CHAPTER 4 Gravitation and."— Presentation transcript:

1 Universe Eighth Edition Universe Roger A. Freedman William J. Kaufmann III CHAPTER 4 Gravitation and the Waltz of the Planets CHAPTER 4 Gravitation and the Waltz of the Planets

2 Reading Assignment – Chapter 5 (The Nature of Light) Homework – Chapter 3 Quiz due Wednesday 9/15 by 9 PM

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11 Epicycles are used in a geocentric model to explain the A. eastward motion of Mars. B. westward motion of Mars. C. phases of Venus. D. appearance of Venus in the early morning or late evening sky. E. phases of the moon. Q4.3

12 Epicycles are used in a geocentric model to explain the A. eastward motion of Mars. B. westward motion of Mars. C. phases of Venus. D. appearance of Venus in the early morning or late evening sky. E. phases of the moon. A4.3

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21 When Jupiter is at opposition (see diagram), it is overhead (i.e., on the meridian) at A. 6:00 A.M. B. 12:00 noon. C. 6:00 P.M. D. midnight. E. never at night. Q4.1

22 When Jupiter is at opposition (see diagram), it is overhead (i.e., on the meridian) at A. 6:00 A.M. B. 12:00 noon. C. 6:00 P.M. D. midnight. E. never at night. A4.1

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31 A planet in an elliptical orbit around the Sun moves most rapidly when it is A. at aphelion. B. at perihelion. C. halfway between perihelion and aphelion. D. closer to aphelion than perihelion. E. None of the above; it has a constant speed. Q4.6

32 A planet in an elliptical orbit around the Sun moves most rapidly when it is A. at aphelion. B. at perihelion. C. halfway between perihelion and aphelion. D. closer to aphelion than perihelion. E. None of the above; it has a constant speed. A4.6

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35 Kepler’s three laws A. were initially derived from fundamental physics laws. B. were initially found from observation and are empirical rules that describe how the planets move. C. were handed down from the ancient Greeks. D. were discovered by Kepler in ancient Babylonian texts. E. are now known to be grossly incorrect. Q4.5

36 Kepler’s three laws A. were initially derived from fundamental physics laws. B. were initially found from observation and are empirical rules that describe how the planets move. C. were handed down from the ancient Greeks. D. were discovered by Kepler in ancient Babylonian texts. E. are now known to be grossly incorrect. A4.5

37 Two planets are in circular orbits around similar stars. Each is the same distance from its parent star. One planet is Jupiter’s size, whereas the other is Earth’s size. Which of the following is true? A. The Jupiter-size planet has a much longer period than the Earth-size planet. B. The Earth-size planet has a much longer period than the Jupiter-size planet. C. Both planets have the same period. D. The Earth-size planet has a period exactly twice that of the Jupiter-size planet. E. Not enough information is given to determine the correct answer. Q4.7

38 Two planets are in circular orbits around similar stars. Each is the same distance from its parent star. One planet is Jupiter’s size, whereas the other is Earth’s size. Which of the following is true? A. The Jupiter-size planet has a much longer period than the Earth-size planet. B. The Earth-size planet has a much longer period than the Jupiter-size planet. C. Both planets have the same period. D. The Earth-size planet has a period exactly twice that of the Jupiter-size planet. E. Not enough information is given to determine the correct answer. A4.7

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53 Which of the following objects has zero acceleration? A. A car just starting out from a stop light B. A car traveling at 70 miles per hour on a long straight interstate highway C. A car exiting an interstate on a curved off-ramp D. A car slowing down for a red light E. A car skidding to a stop to avoid an accident Q4.9

54 Which of the following objects has zero acceleration? A. A car just starting out from a stop light B. A car traveling at 70 miles per hour on a long straight interstate highway C. A car exiting an interstate on a curved off-ramp D. A car slowing down for a red light E. A car skidding to a stop to avoid an accident Q4.9

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62 The tidal force of the Moon on the Earth occurs because A. the Moon pulls more strongly on the near side of the Earth than the far side of the Earth. B. the Moon pulls more strongly on the far side of the Earth than the near side of the Earth. C. the Moon pulls equally strongly on the near side and the far side of the Earth. D. the Moon keeps its same face toward the Earth. E. the Moon is in a synchronous orbit. Q4.14

63 The tidal force of the Moon on the Earth occurs because A. the Moon pulls more strongly on the near side of the Earth than the far side of the Earth. B. the Moon pulls more strongly on the far side of the Earth than the near side of the Earth. C. the Moon pulls equally strongly on the near side and the far side of the Earth. D. the Moon keeps its same face toward the Earth. E. the Moon is in a synchronous orbit. A4.14

64 Key Ideas Copernicus’s Heliocentric Model: Copernicus’s heliocentric (Sun-centered) theory simplified the general explanation of planetary motions. Copernicus’s Heliocentric Model: Copernicus’s heliocentric (Sun-centered) theory simplified the general explanation of planetary motions. In a heliocentric system, the Earth is one of the planets orbiting the Sun. In a heliocentric system, the Earth is one of the planets orbiting the Sun. A planet undergoes retrograde motion as seen from Earth when the Earth and the planet pass each other. A planet undergoes retrograde motion as seen from Earth when the Earth and the planet pass each other. The sidereal period of a planet, its true orbital period, is measured with respect to the stars. Its synodic period is measured with respect to the Earth and the Sun (for example, from one opposition to the next). The sidereal period of a planet, its true orbital period, is measured with respect to the stars. Its synodic period is measured with respect to the Earth and the Sun (for example, from one opposition to the next).

65 Key Ideas Apparent Motions of the Planets: Like the Sun and Moon, the planets move on the celestial sphere with respect to the background of stars. Most of the time a planet moves eastward in direct motion, in the same direction as the Sun and the Moon, but from time to time it moves westward in retrograde motion. Apparent Motions of the Planets: Like the Sun and Moon, the planets move on the celestial sphere with respect to the background of stars. Most of the time a planet moves eastward in direct motion, in the same direction as the Sun and the Moon, but from time to time it moves westward in retrograde motion. The Ancient Geocentric Model: Ancient astronomers believed the Earth to be at the center of the universe. They invented a complex system of epicycles and deferents to explain the direct and retrograde motions of the planets on the celestial sphere. The Ancient Geocentric Model: Ancient astronomers believed the Earth to be at the center of the universe. They invented a complex system of epicycles and deferents to explain the direct and retrograde motions of the planets on the celestial sphere.

66 Key Ideas Kepler’s Improved Heliocentric Model and Elliptical Orbits: Copernicus thought that the orbits of the planets were combinations of circles. Using data collected by Tycho Brahe, Kepler deduced three laws of planetary motion. Kepler’s Improved Heliocentric Model and Elliptical Orbits: Copernicus thought that the orbits of the planets were combinations of circles. Using data collected by Tycho Brahe, Kepler deduced three laws of planetary motion. (1) the orbits are in fact ellipses (1) the orbits are in fact ellipses (2) a planet’s speed varies as it moves around its elliptical orbit (2) a planet’s speed varies as it moves around its elliptical orbit (3) the orbital period of a planet is related to the size of its orbit. (3) the orbital period of a planet is related to the size of its orbit.

67 Key Ideas Evidence for the Heliocentric Model: The invention of the telescope led Galileo to new discoveries that supported a heliocentric model. These included his observations of the phases of Venus and of the motions of four moons around Jupiter. Evidence for the Heliocentric Model: The invention of the telescope led Galileo to new discoveries that supported a heliocentric model. These included his observations of the phases of Venus and of the motions of four moons around Jupiter. Newton’s Laws of Motion: Isaac Newton developed three principles, called the laws of motion, that apply to the motions of objects on Earth as well as in space. Newton’s Laws of Motion: Isaac Newton developed three principles, called the laws of motion, that apply to the motions of objects on Earth as well as in space.

68 Key Ideas (1) the tendency of an object to maintain a constant velocity, (1) the tendency of an object to maintain a constant velocity, (2) the relationship between the net outside force on an object and the object’s acceleration, (2) the relationship between the net outside force on an object and the object’s acceleration, and (3) the principle of action and reaction. and (3) the principle of action and reaction. These laws and Newton’s law of universal gravitation can be used to deduce Kepler’s laws. They lead to extremely accurate descriptions of planetary motions. These laws and Newton’s law of universal gravitation can be used to deduce Kepler’s laws. They lead to extremely accurate descriptions of planetary motions. The mass of an object is a measure of the amount of matter in the object. Its weight is a measure of the force with which the gravity of some other object pulls on it. The mass of an object is a measure of the amount of matter in the object. Its weight is a measure of the force with which the gravity of some other object pulls on it.

69 Key Ideas In general, the path of one object about another, such as that of a planet or comet about the Sun, is one of the curves called conic sections: circle, ellipse, parabola, or hyperbola. In general, the path of one object about another, such as that of a planet or comet about the Sun, is one of the curves called conic sections: circle, ellipse, parabola, or hyperbola. Tidal Forces: Tidal forces are caused by differences in the gravitational pull that one object exerts on different parts of a second object. The tidal forces of the Moon and Sun produce tides in the Earth’s oceans. The tidal forces of the Earth have locked the Moon into synchronous rotation.


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