Astr - Chapter 02a & 02b
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.
According to Copernicus, the retrograde motion for Mars must occur
at opposition, when the earth overtakes Mars and passes between Mars and the Sun.
A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years?
square root of 27
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.
Which of these observations of Galileo refuted Ptolemy's epicycles?
the complete cycle of Venus' phases
The greatest contribution of the Greeks to modern thought was:
the development of scientific inquiry and model building.
If the distance between two asteroids is doubled, the gravitational force they exert on each other will
be one fourth as great.
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.
Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as
elliptical, not circular.
Tycho Brahe's contribution to Kepler's Laws of Planetary Motion were
his detailed and accurate observations of the planet's position
The force of gravity between two objects:
increases with the masses of the bodies, but decreases with the square of the distances between them.
According to Copernicus, retrograde motion for Venus must occur around
inferior conjunction, when it passes between us and the Sun.
The Ptolemaic model probably persisted for all these reasons EXCEPT:
it accounted well for Galileo's observations of the phase cycle of Venus.
Escape velocity is the speed required to
overcome the gravitational pull of an object.
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
Combining Newton's and Kepler's laws, we can weigh the Sun, provided we know:
the size of the A.U. and exact length of the year.
Scientists today do not accept the Ptolemaic model because:
the work of Tycho and Kepler showed the heliocentric model was more accurate.
Geosynchronous satellites orbit at about four earth radii, where the earth's gravitational pull is?
to follow
Geosynchronous satellites orbit at about four earth radii, where the earth's gravitational pull is:
1/16 g.
How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU?
100X
Kepler's second law implies what about planetary motion?
A planet moves faster when it is closer to the Sun.
Upon which point do Copernicus and Kepler disagree?
The orbits of the planets are ellipses, with one focus at the Sun.
Which of the statements below is part of both the Ptolemaic and Copernican models?
The Moon orbits the Earth once a month.
A fatal flaw with Ptolemy's model is its inability to predict the observed phases of
Mercury and Venus.
Which of these was NOT a part of the original Copernican model?
Mercury speeds up at perihelion, and slows down at aphelion
A circular orbit would have an eccentricity of
0.
Which concept was NOT a part of Kepler's Laws of Planetary Motion?
Epicycles are needed to explain the varying brightnesses of the planets.
Which was a contribution to astronomy made by Copernicus?
He laid out the order and relative motion of the known solar system.
What contribution to astronomy was made by Tycho Brahe?
His observations of planetary motion with great accuracy proved circular orbits could not work.
The Law of Universal Gravitation was developed by:
Newton.
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.
The most accurate Greek attempt to explain planetary motion was the model of:
Ptolemy
