Astronomy Exam Chp 3&4

Kepler's first law states that a planet moves around the Sun in a(n)

elliptical orbit, with the Sun at one focus

What fundamental belief about the universe, established by the Greeks and adopted by the early Christian church, was shattered by Galileo's observation of moons orbiting Jupiter?

everything in the universe orbits the Earth

When observing planetary motions from the Earth, the phrase direct motion refers to the

slow eastward motion of the planet from night to night compared to the background stars

keplers 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 tern 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 semi major axis of an ellipse is

the distance from the center of the ellipse to one end, along the largest diameter of the ellipse

Kepler's third law can be described in which of the following ways?

The larger the orbit of a planet, the longer the planet takes to complete one revolution

The major contribution of Tycho Brahe to the development of modern astronomy was

measuring planetary positions very accurately

in the geocentric model of the solar system, which one of the following phases of Venus should be visible from Earth?

new

he sidereal period of a planet is defined as the time between two successive

passages of the planet in front of a particular point in the sky (e.g., a star) as seen from the Sun

Kepler's third law, the harmonic law, provides a relationship between a planet's orbital

period and the length of the semimajor axis

To which point in a planetary orbit does the word perihelion refer?

point closest to the Sun

To which point in a planetary orbit does the word aphelion refer?

point furthest from the Sun

An apparent westward motion of a planet from night to night compared to the background stars (as viewed from the Earth) is referred to as

retrograde motion

What was the most important difference between the development of Isaac Newton's theory of planetary motion and that of Johannes Kepler?

Newton developed his theory from basic physical assumptions, whereas Kepler simply adjusted his theory to fit the data

What was the most important contribution of Newton to the development of astronomy?

Newton showed that astronomical phenomena can be explained using only basic physics and mathematics.

Why were Newton's three laws so important to astronomy?

Newton's laws showed that planets can move around the Sun by themselves forever, without coming to rest.

the time period between two successive passages of a planet past a particular star as seen from the Sun is its

sidereal period

A comet is observed to return to the vicinity of the Sun on a long elliptical orbit with a period of 31.7 years. What is the semimajor axis of the orbit?

10 AU

A diver weighing 138 pounds has just dived up and out from the high board and is doing a back flip before starting to descend toward the water. How much force does the diver exert on the Earth while doing the back flip?

138 pounds

Halley's Comet returns to the Sun's vicinity approximately every 76 years in an elliptical orbit. According to Kepler's third law, what is the semimajor axis of this orbit?

17.9 AU

If a planet were to exist in our solar system in a circular orbit with a radius of 3 AU, about how long would it take to orbit the Sun once?

5.2 years

The Sun exerts a gravitational pull on Earth. Why doesn't Earth fall into the Sun?

Earth is moving across the Earth-Sun direction, so Earth is pulled around in a circle.

The law of gravitation expounded 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/R2.

the planets that were known before the telescope was invented were

Saturn, Venus, Mars, Mercury, and Jupiter

The Copernican system for planetary motions is

Sun-centered, with the planets moving in perfect circles around the Sun

Which of the following observations of the motions of the large moons of Jupiter did Galileo find most significant?

The moons farther from Jupiter had longer periods, just as Copernicus had discovered for the planets around the Sun.

Which of the following descriptions 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 gravitational force of the Sun.

Which of the following sentences correctly states the significance of Galileo's observation that Jupiter has satellites (moons)?

The observation showed that Jupiter must be four times the size of the Earth (because Jupiter has four moons and the Earth has one).

What did Galileo NOT observe with his new telescope?

Uranus

If an object has an orbit around the Sun that has an eccentricity of 0.8, then the orbit is

a long, thin ellipse

from the earth, we observe occasional retrograde motion in the motion of

all the planets

If an object has an orbit around the Sun that has an eccentricity of 0.1, then the orbit is

almost circular, but not quite

an object orbiting the Sun in a circle can be said to be

always accelerating

According to Newton's second law of motion, an object acted on by a constant force

always moves with a constant acceleration.

At what point in a planetary orbit is the planet's speed the slowest?

at aphelion

When viewed from the Earth, the celestial sphere (the background of stars) moves east to west on a daily basis. This motion is caused by the

rotation of the earth on its axis

Nicolaus Copernicus was the first person to

develop a comprehensive model for a Sun-centered solar system

An apparent eastward motion of a planet from night to night compared to the background stars (as viewed from the Earth) is referred to as

direct motion

A significant contribution of Kepler to our understanding of the solar system was the

discovery that planetary orbits are not circular

Which of the following pairs of forces is an example of an action-reaction pair by Newton's third law?

for a dog pulling on its leash, the force of the dog on the leash and the force of the leash on the dog

newton's second law states that

force equals mass times acceleration

a body whose velocity is constant

has zero acceleration

according to Newton's first law

if no net force is acting on an object, then both the objects speed and direction of travel will be constant

In which direction would the Earth move if the Sun's gravitational force were suddenly removed from it?

in a straight line along a tangent to its circular orbit

Kepler's second law states that a planet moves fastest when it

is closest to the Sun

The eccentricity of a planet's orbit describes

its shape compared to that of a circle

The time period between two successive passages of a planet through the position of opposition is

its synodic

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

Suppose two asteroids are located at the same distance from the Sun. One asteroid has twice the mass of the other. According to Newton's law of gravitation (and ignoring all forces except that from the Sun),

the more massive asteroid feels twice the force that the other does.

Galileo's early observations of the sky with his newly made telescope included the discovery of

the phases of Venus

The time interval between two successive repeated positions of a planet with respect to the Sun and the Earth in its orbit, such as conjunction to conjunction, is known as

the planet's synodic period

According to Newton's third law, if a force is acting on an object, then

there must be some other force acting on a different object, with the same magnitude but in the opposite direction

the acceleration of a moving body is defined as the rate of change of

velocity with time

the word planet is derived from a Greek term meaning

wanderer

In the simplified version of Kepler's third law, P2 = a3, the units of the orbital period P and the semimajor axis of the ellipse a must be, respectively,

years and astronomical units