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29 Cards in this Set
- Front
- Back
Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as: |
elliptical, not circular. |
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Tycho Brahe's contribution to Kepler's Laws of Planetary Motion was: |
his detailed and accurate observations of the planet's position. |
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A circular orbit would have an eccentricity of: |
0 |
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Upon which point do Copernicus and Kepler disagree? |
The orbits of the planets are ellipses, with one focus at the Sun. |
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According to Kepler's third law, the square of the planet's period in years is: |
proportional to the cube of its semimajor axis in A.U. |
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What does Kepler's third law imply about planetary motion? |
Planets further from the Sun orbit at a slower speed than planets closer to the Sun. |
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A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years? |
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A calculation of how long it takes a planet to orbit the Sun would be most closely related to Kepler's
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third law of planetary distances.
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An asteroid with an orbit lying entirely inside Earth's
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has an orbital semimajor axis of less than 1 AU.
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If Earth's orbit around the Sun were twice as large as it is now, the orbit would take |
more than two times longer to traverse |
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Today we rely largely on what technique to precisely measure distances in the solar system? |
radar echo timings |
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The force of gravity varies with the |
both product of the two masses and inverse square of the distance separating the two bodies |
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The Law of Universal Gravitation was developed by |
Newton. |
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According to Newton's Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would: |
decrease by a factor of 9. |
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How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU? |
100X
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Which of these was a contribution of Newton to astronomy? |
-The Sun's gravity is greatest on a planet at perihelion, so the planet must speed up. -His differential calculus lets us calculate planetary motions more accurately. -The Moon pulls as strongly on us as we do on it. -Artificial satellites could be put into orbit about the Earth |
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Geosynchronous satellites orbit at about four Earth radii, where the Earth's gravitational pull is |
1/16 g. |
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Jupiter lies about 5 A.U. from the Sun, so at its distance: |
the Sun's gravity is 25 times weaker than its pull on the Earth. |
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Given that the planet orbiting the nearby star 51 Pegasi is about 20X larger than the Earth, but 400X more massive, on that world you would weigh: |
the same as you do here |
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If the distance between two asteroids is doubled, the gravitational force they exert on each other will |
be one fourth as great. |
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Newton's Law of Gravity would explain why Saturn, so far from the Sun, moves so slowly across the sky. |
true |
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Compared to orbital velocity, escape velocity is about: |
40% more. |
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Orbital speed is the speed with which a planet moves around the Sun. This speed is determined by |
the mass of both the planet and the Sun and the distance between the two. |
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Escape velocity is the speed required to: |
overcome the gravitational pull of an object. |
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If the Sun and its mass were suddenly to disappear, Earth would |
fly off into space |
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Figure 2.26(b) in the textbook ("Orbits") shows the orbits of two stars of unequal masses. If one star has twice the mass of the other, then the more massive star |
moves more slowly than the less massive star. |
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Two otherwise isolated bodies of equal mass will orbit in which of the following configurations as viewed from a fixed distant point? |
They would orbit each other in identical but oppositely directed ellipses that share a common focus. |
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In what way did Newton improve Kepler's laws? |
He discovered the dependence on mass in the third law. |
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According to Newton, planets orbit in ellipses with what at the two foci? |
The center of mass and nothing |