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)