Why do scientists think that our solar system must have formed sometime after nearby supernovae explosions?
A) existence of heavy elements
B) solar temperature too low
C) our Sun is a G-type star
D) They don't—scientists believe our Sun is among the first generation of stars.
A
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When an atom emits light, an electron in it moves from a higher to a lower energy level.
Answer the following statement true (T) or false (F)
Is a fuel-cell vehicle properly described as a "heat engine"?
A) Yes, because it uses thermal energy to produce electricity. B) Yes, because it uses chemical energy to create electric energy. C) Yes, because it uses thermal energy to do work. D) No, because it converts chemical energy directly to electric energy. E) No, because it converts electric energy directly into chemical energy.
The six face-centered lattice points of a FCC lattice unit cell contribute ______________lattice point(s) to a unit cell.
Fill in the blank(s) with the appropriate word(s).
A ball is dropped from a rooftop of a building and falls for two seconds. The acceleration of gravity is 9.8 m/s2 . The ball is referred to at the two-second time. The distance the ball is below the rooftop in meters is
a. 0. b. 4.9. c. 9.8. d. 19.6. e. none of these.