One ancient Greek scientist, Aristarchus, had a theory about the layout of the universe that was quite different from the other Greek theories. According to Aristarchus's theory,
A) Earth is at the center and other objects move around Earth in simple circles.
B) the sun is at the center and other objects, including Earth, move around the sun in simple circles.
C) Earth is at the center, and the planets move around Earth in orbits that could be described as "circles-within-circles" or "loop-the-loops."
D) the Earth is held up by Hercules, who stands on a turtle, who stands on an elephant, who stands on Zeus, who is beginning to think that the whole thing isn't worth the effort.
E) there is no fixed center anywhere in the universe.
B
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NASA satellites stay up because
A) they are moving so fast that they are able to "fall" around Earth. B) their rocket engines hold them above Earth's surface. C) there is no air resistance in outer space and thus no downward force on an orbiting satellite. D) they are away from Earth's gravity and thus do not get pulled down toward Earth. E) centrifugal force pulls outward on them.
A particle (charge = 5.0 mC) is released from rest at a point x = 10 cm. If a 5.0-mC charge is held fixed at the origin, what is the kinetic energy of the particle after it has moved 90 cm?
a. 1.6 J b. 2.0 J c. 2.4 J d. 1.2 J e. 1.8 J
A series RC circuit has a time constant of 0.900 s. The battery has an emf of 24.0 V, and the maximum current in the circuit is 0.500 mA.What is the capacitance?
a. 1.80 ?F b. 43.2 ?F c. 18.8 ?F d. 53.3 ?F
Infrared radiation emitted by Earth’s surface
a. heats the troposphere from below. b. causes convection. c. causes weather (storms). d. all of the above. e. none of the above.