Chapter 3- practice
C
When we say that a planet has a highly eccentric orbit, we mean that: A. it is spiraling in toward the Sun. B. its orbit is an ellipse with Sun at one focus. C. in some parts of its orbit it is much closer to the Sun than in other parts.
1 arcminute
less than the thickness of a fingernail viewed at arm's length
Pseudoscience
"fake science"
Eccentricity
a measure of how much an ellipse deviates from a perfect circle
Hypothesis
an educated guess
Kepler's Laws of planetary motion
1. The orbit of each planet around the sun is an ellipse with the sun at one focus. 2. As a planet moves around its orbit, it sweeps out equal areas in equal times. 3. More distance planets orbit the sun at slower average speeds obeying a precise mathematical relationship A planet with a perfectly circular orbit would orbit at constant speed. ... No, they do not revolve at constant speed. The planets orbits, according to Kepler's laws, are elliptical. when the planet reaches closer to the sun, it is moving faster as compared to when it is farther from the sun.
C
Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler's second law: A. Earth travels faster in its orbit around the Sun in July than in January. B. It is summer in January and winter in July. C. Earth travels faster in its orbit around the sun in January than in July.
B
From Kepler's third law, a hypothetical planet that is twice as far from the Sun as Earth should have a period of A. ½ Earth year. B. more than 2 Earth years. C. 2 Earth years. D. 1 Earth year. E. It depends on the planet's mass.
A
From Kepler's third law, an asteroid with an orbital period of 8 years lies at an average distance from the Sun equal to A. 4 astronomical units B. 2 astronomical units C. 8 astronomical units D. 16 astronomical units E. It depends on the asteroid's mass.
Ptolemy
He developed a system for predicting planetary positions that remained in use for some 1500 years.
Galileo
He discovered that Jupiter has moons.
Kepler
He discovered that the orbits of planets are ellipses.
Tycho Brahe
He was the first to prove that comets lie beyond Earth's atmosphere.
A
Kepler's second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that A. a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun. B. a planet's period does not depend on the eccentricity of its orbit. C. the period of a planet does not depend on its mass. D. planets that are farther from the Sun move at slower average speeds than nearer planets. E. planets have circular orbits.
D
Kepler's third law, p^2 = a^3, means that A. the period of a planet does not depend on its mass. B. A planet's period does not depend on the eccentricity of its orbit. C. all orbits with the same semimajor axis have the same period. D. planets that are farther from the Sun move at slower average speeds than nearer planets. D. All of the above are correct.
Ptolemaic model
Ptolemy's geocentric model; each planet moved around Earth on a small circle that turned upon a larger circle; correctly forecast future planetary positions to within a few degrees of arc
newton
The force of gravity on an object is weight. Mass is the amount of matter and does not ever change (mass does). Friction acts to slow down objects and occurs when objects resist change.
False
True or False: Scientific thinking developed only in the past few decades.
A
What is meant by a hypothesis? A. an explanation for a phenomenon that makes a prediction B. A natural phenomenon that requires explanation C. a tentative understanding of a natural phenomenon D. a historical theory that has been proved inaccurate E. a pseudoscientific idea
A
Which of the following is not true about a scientific theory? A. A theory is essentially an educated guess. B. Even the strongest theories can never be proved true beyond all doubt. C. A theory must explain a wide range of observations or experiments.
B
Which of the following is not true about scientific progress? A. Science progresses through the creation and testing of models of nature. B. Science advances only through the scientific method. C. Science avoids explanations that invoke the supernatural.
B
Which of the following statements about scientific theories is not true? A. A theory is a model designed to explain a number of observed facts. B. A theory cannot be taken seriously by scientists if it contradicts other theories developed by scientists over the past several hundred years. C. A theory can never be proved beyond all doubt; we can only hope to collect more and more evidence that might support it. D. If even a single new fact is discovered that contradicts what we expect according to a particular theory, then the theory must be revised or discarded. E. A theory must make predictions that can be checked by observation or experiment.
Scientific model
a conceptual representation created to explain and predict observed phenomena; may not fully explain all our observations of nature
Paradigm
a general pattern of thought that tends to shape scientific study during a particular time period
Theory
a model of some aspect of nature that has been rigorously tested and has passed all tests to date
Ellipse
a type of oval that happens to be the shape of bound orbits. Can be drawn by moving a pencil along a string whose ends are tied to two tacks
Semimajor axis
half the distance across the long axis of an ellipse
Geocentric model
placed a spherical Earth at the center of the universe
Copernican revolution
the dramatic change, initiated by Copernicus, that occurred when we learned that Earth is a planet orbiting the Sun rather than the center of the universe
Perihelion
the point at which an object orbiting the sun is closest to the sun
Aphelion
the point at which an object orbiting the sun is farthest from the sun
Foci
two special points within an ellipse that lie along the major axis; the point around which we could stretch a pencil and string to draw an ellipse; when one object orbits a second object, the second object lies at on focus of the orbit
