The brilliant nuclei of Seyfert galaxies change brightness rapidly, in only a few hours or minutes, especially at _____
A) microwave wavelengths
B) visible light wavelengths
C) gamma ray wavelengths
D) X-ray wavelengths
D
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Because of Earth's rotation, a swinging pendulum rotates about a vertical axis once every twenty-four hours.
a. true b. false
Microscopic slush in water tends to make the water
A) more dense. B) less dense. C) slipperier. D) warmer.
What is the length of a simple pendulum with a period of 2.0 s?
A) 20 m B) 0.99 m C) 1.2 m D) 1.6 m E) 0.87 m
Newton concluded that a force from the Earth had to act on the moon because
a. a force is needed to keep the moon in motion in its orbit. b. a force is needed to pull the moon outward. c. a force is needed to accelerate the moon toward Earth away from straight-line motion. d. the moon moved at a constant velocity in a straight line. e. all of the above