physics quiz 4
who was the first astronomer to use a telescope for viewing the sky?
Galileo
the first comet to have it orbit predicted (using Isaac Newton's Laws of motion and gravity) was later named
Halley's Comet
the greek mathematician Ptolemy devised a
geocentric model for the solar system
the eccentricity of a planet's orbit describes
its shape compared to that of a circle
which of the following situations describes an acceptable path for a body gravitationally bound to the Sun?
long ellipse, with the Sun at one focus of the ellipse
the force of gravity between two objects a fixed distance part is proportional to the
product of their masses
Kepler's third law, as derived by Newton from the law of gravitation, applies
to all situations where two objects orbit each other solely under the influence of their mutual gravitational attraction
on a star chart plotting the position of the Sun and Venus with north up, if Venus is visible at greatest elongation at sunset then Venus on the star hart should be found
to the left of the sun on the chart near the line on the chart representing the ecliptic
the acceleration of a moving body is defined as the rate of change of
velocity with time
If a tenth planet (tentatively predicted to exist on the basis of perturbations in the orbits of Uranus and Neptune) were to be discovered with a sidereal period of 200 years, what would be the radius of its orbit (assumed to be circular)?
25 AU
before deriving the shapes of planetary orbits, Johannes Kepler worked as an assistant to
Tycho Brahe
the law of gravitation expanded by Newton for the force F between two objects of masses M and m with separation (between centers) of R is given, with G being a constant, by
F = GMm/R^2
Newton's second law states that
Force equals mass times acceleration
what was the most important contribution of Newton to the development of astronomy?
Newton showed that astronomical phenomena can be explained using on basic physics and mathematics
the simplified version of Kepler's third law of planetary motion related the period P (in sidereal years) to the length of the semimajor axis a (in astronomical units) in which way?
P^2=1/a^2
The planets that were known before the telescope was invented were
Saturn, Venus, Mars, Mercury, and Jupiter
the model of the solar system that Johannes Kepler proposed was
Sun-Sintered, with elliptical planetary orbits
the copernican system for planetary motions is
Sun-centered, with the planets moving in perfect circles around the Sun.
Copernicus lived
after Ptolemy but before Kepler.
according to Galileo's observations of Venus, when Venus is at full phase, its angular size
and angular distance from the Sun are both minimum
at which point in a planet's elliptical orbit is the planet farthest from the sun?
aphelion
the one significant observation Galileo made through his home-built telescope that convinced him that the planets revolved around the Sun was the
appearance of Venus following a cycle of phases, from crescent through quarter and gibbous phases to full
To which point in a planetary orbit is the planet's speed the slowest?
at aphelion
Where is a planet when it is moving most rapidly in its orbit?
at perihelion
the "Almagest" is a(n)
collection of ancient data and predictions of positions of the Sun, the moon , and the planets, complied by Ptolemy
Nicolaus Copernicus was the first person to
develop a comprehensive model for a Sun-centered solar system.
suppose that an object is discovered orbiting the Sun once every 120 years. Which of the following paths is possible orbit for this object?
ellipse
Kepler's first law states that the orbit of a planet about the Sun is a(n)
ellipse with the Sun at one focus
how many moons of Jupiter did Galileo see?
four
the best time(s) to see inferior planets from the Earth is (are) when these planets are at positions of
greatest elongation
a body whose velocity is constant
has zero acceleration
when Mars is at opposition, it is
high in the sky at midnight
according to Newton's first law,
if no net force is acting on an object, then both the object's speed and direction of travel will be constant.
the law of gravity is called an inverse square law because
if you half the distance between two masses the force goes up by a factor of 4
in which direction would the Earth move if the Sun's gravitational force as suddenly removed from it?
in a straight line along a tangent to its circular orbit
Kepler's second law states that a plane moves fastest when it
is closest to the sun
the major contribution of Tyco Brahe to the development of modern astronomy was
measuring planetary positions very accurately
an object is on an orbit due to its gravitational attraction to the Sun. if there are no other forces acting on the object except the pull of the sun, then Newton's Laws priest that the orbit
might be an ellipse, a parabola, or a hyperbola depending how fast the object is moving on the orbit
The purpose of describing planetary orbits in terms of epicycles and deferents was to account for
pattern of alternating direct and retrograde motion
The motions of the planets against the background stars in our sky can best be described as
regular patterns with general eastward motion interrupted by the periods of western motion
to specify an object;s velocity completely, we need to specify its
speed and direction of travel
the main difference between the concepts of speed and velocity is that
speed is "how fast" but velocity is "how fast" and "what direction"
Kepler's third law tells us that the
square of a planet's period in years is the same number as the cube of its semimajor axis in AU.
Kepler's second law states that a line joining a planet to the Sun
sweeps out equal areas in equal times
The term "retrograde motion" for a planet refers to the
temporary reversal of the planet's normal west-to-east motion past the background stars as seen from the Earth
the distance from the perihelion point to the aphelion point of a planetary orbit is
the major axis
Why did Galileo's observations of moons orbiting Jupiter disagree with the theory of the universe accepted up to that time in history?
the moons did not orbit the Earth
which of the following description characterizes the Newtonian understanding of the mechanics of the solar system?
the natural motion of the planets is motion in a straight line. The planets are prevented from straight-line motion by the inward gravitational force of the Sun
In which part of the sky does Venus appear at sunset when it is at greatest elongation?
the western sky
the word "planet: is derived from a greek term meaning
wanderer
the terms inferior and superior applied to the planets in the solar system refer to
whether the planet is closer to the sun or further from the sun than the Earth is its orbit
according to Newton's first law, is motion on a curved path accelerated motion?
yes, a curved path implies that a force acts on the body
a distant asteroid is discovered that takes 50 years to orbit the Sun once. According to Kepler's third law, what is the average distance of this asteroid from the Sun?
13.6 AU (cube root of 2500)
Halley's Comet returns to the Sun's vicinity approximately every 76 years in an elliptical orbit. According to Kepler's third law, what will be the semi-major axis of this orbit?
17.9 AU
A space probe is put into a circular orbit around the Sun at a distance of exactly 2 AU from the Sun. According to Kepler's third law, how long does it take this probe to orbit the Sun once?
2.8 years (square root of 8)