The reason a life jacket helps keep you afloat is
A) the jacket makes you weigh less.
B) the jacket has the same density as an average human.
C) the jacket repels water.
D) if you sink, the jacket sinks.
E) the density of both you and the jacket together is less than your density alone.
Answer: E
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Briefly describe the four possible expansion patterns of the universe
What will be an ideal response?
Why did the solar nebula heat up as it collapsed?
A) As the cloud shrank, its gravitational potential energy was converted to thermal energy. B) Collisions among planetesimals generated friction and heat. C) Radiation from other nearby stars that had formed earlier heated the nebula. D) Nuclear fusion occurring in the core of the protosun produced energy that heated the nebula. E) The shock wave from a nearby supernova heated the gas.
Radioactive decay is involved in
a. irradiating food to destroy harmful bacteria b. keeping the interior of the Earth hot c. making smoke detectors work d. finding flaws in jet engine parts e. all of the above
Our primary reason for studying the theories of Ptolemy, Copernicus, and Kepler in this course is
A) to learn some history of physics and astronomy. B) to learn about the methods and the validity of science. C) so that we can understand the structure of our solar system. D) to see how these early theories of atomic physics compare with more recent studies. E) as a foundation for our later study of Newtonian physics.