Interstellar gas is composed of
A) only hydrogen.
B) 90% hydrogen, 9% helium by weight.
C) 10% hydrogen, 90% helium by numbers of atoms.
D) some hydrogen, but mainly carbon dioxide.
E) ammonia, methane, and water vapor.
B
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How does Earth's varying distance from the Sun affect our seasons?
A) It doesn't—Earth's orbital distance plays no significant role in the seasons. B) It causes the seasons to be more extreme than they would be if the Earth's distance from the Sun were always the same. C) It makes summer warmer in the Northern Hemisphere than in the Southern Hemisphere. D) It is responsible for the fact that the seasons are opposite in the Northern and Southern hemispheres.
Matter Waves: Calculate the kinetic energy, in electron-volts, of a neutron that has a de Broglie wavelength of 7.2 × 10-12 m (mneutron = 1.675 × 10-27 kg, 1 eV = 1.6 × 10-19 J, h = 6.626 × 10-34 J ? s)
Fill in the blank(s) with the appropriate word(s).
Hardness is a comparative property that refers to the ability of a mineral to resist
a. fracturing. b. cleaving. c. scratching. d. crushing.
A fast-moving missile soaring overhead possesses
A) speed. B) force. C) both of these D) neither of these