Which of the following are the two key starting assumptions of theoretical models of galaxy evolution?
A) (1) The beginning of the universe can be modeled as a giant supernova explosion and (2) this supernova created all the elements in the proportions we find them today.
B) (1) Hydrogen and helium gas, along with dark matter, filled all of space and (2) some regions of the universe were slightly denser than others.
C) (1) Hydrogen and helium gas, along with dark matter, filled all of space and (2) the distribution of this material was perfectly uniform everywhere.
D) (1) Hydrogen gas, along with dark matter, filled all of space and (2) all the other elements came from stars.
B) (1) Hydrogen and helium gas, along with dark matter, filled all of space and (2) some regions of the universe were slightly denser than others.
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A goldfish bowl is spherical, 8.0 cm in radius. A goldfish is swimming 3.0 cm from the wall of the bowl. Where does the fish appear to be to an observer outside? The index of refraction of water is 1.33
Neglect the effect of the glass wall of the bowl. A) 3.3 cm inside the bowl B) 3.9 cm inside the bowl C) 2.5 cm inside the bowl D) 3.0 cm inside the bowl E) 1.7 cm inside the bowl
Heat is a form of energy, and it has long been known that heat energy will naturally flow
A. from solids to liquids, but only when the solid is melting. B. from hot to cold objects. C. from cold to hot objects. D. from liquids to solids, except when the solid is melting.
In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder-size objects. Which of the following real things in our solar system would look most like such science fiction dangers?
A) the rings of Saturn B) the asteroid belt C) the Oort cloud D) the atmosphere of Jupiter
A jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J. The efficiency of the jack system is
A) 10%. B) 20%. C) 50%. D) 80%. E) need more information