One star has a surface temperature of 6000 K and another has a surface temperature of 7000 K
If the two stars have the same absolute luminosity, and if the radius of the 6000 K star is R6 and the radius of the 7000 K star is R7, what is the ratio R6/ R7? A)
0.7
B)
1.2
C)
1.4
D)
1.6
E)
1.9
C
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A possible means for making an airplane radar-invisible is to coat the plane with an antireflective polymer. If radar waves have a wavelength of 6.00 cm, and the index of refraction of the polymer is n = 1.68, how thick would the coating be if a 180° phase change occurs at both surfaces?
a. 17.9 mm b. 35.7 mm c. 8.93 mm d. 4.46 mm e. 25.2 mm
Charge of uniform density (0.30 nC/m2) is distributed over the xy plane, and charge of uniform density (?0.40 nC/m2) is distributed over the yz plane. What is the magnitude of the resulting electric field at any point not in either of the two charged planes?
a. 40 N/C b. 34 N/C c. 28 N/C d. 46 N/C e. 6.0 N/C
Two astronauts, of masses 60. kg and 80. kg, are initially at rest in outer space. They push each other apart. What is their separation after the heavier astronaut has moved 12. m?
A) 21. m B) 24. m C) 16. m D) 9. m E) 28. m
You are once again in a hot, dense place. You are surrounded by protons and neutrons, some rapidly fusing into helium. You notice that your surroundings are cooling (good, because it's really hot!) and rapidly dropping in density
Within about 3 minutes, the fusion reactions stop. Where are you? A) You are in the center of a star very much like our Sun. B) You are in the early universe during the era of nucleosynthesis. C) You are inside a nuclear power plant on Earth. D) You are in the center of a star much smaller than the Sun. E) You are in the center of a massive star near the end of its life.