What happened to the quarks that existed freely during the particle era?
A) They combined to make protons, neutrons, and their antiparticles.
B) They froze out of the soup of particles at the end of the era.
C) They evaporated.
D) They combined to make electrons and neutrinos.
E) They combined to make W and Z bosons.
A) They combined to make protons, neutrons, and their antiparticles.
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Only one of the statements below uses the term theory in its correct, scientific sense. Which one?
A) Einstein's theory of relativity has been tested and verified thousands of times. B) Evolution is only a theory, so there's no reason to think it really happened. C) I have a new theory about the cause of earthquakes, and I plan to start testing it soon. D) I wrote a theory that is 152 pages long.
For a furnace to provide 50,000 Btu/hr of thermal energy to a living space, what should the rate of heat supplied by the fuel if the furnace efficiency is 75%?
a. 25,000 b. 37,000 c. 50,000 d. 67,000 e. 125,000 Btu/hr
The period of Jupiter's orbit around the Sun is approximately 12 years. What is the approximate distance from the Sun to Jupiter?
a. 144 AU b. 1728 AU c. 42 AU d. 5.2 AU e. 2.3 AU
As I slide a box at constant speed up a frictionless slope, pulling parallel to the slope, the tension in the rope will be:
a. greater than the tension would be if the box were stationary. b. greater than the weight of the box. c. equal to the weight of the box. d. less than the weight of the box.