As a basketball player starts to jump for a rebound, he begins to move upward faster and faster until he leaves the floor. During this time that he is in contact with the floor, the force of the floor on his shoes is:
a. bigger than his weight.
b. equal in magnitude and opposite in direction to his weight.
c. less than his weight.
d. zero.
A
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What prevents a large piece of uranium ore from going naturally into a chain reaction?
a. Because none of its nuclei fission without bombardment from human-controlled sources. b. Because even a small chunk is too large to sustain a chain reaction. c. Because the sample is not large enough to capture many neutrons. d. Because there isn't enough uranium for fissioning neutrons to trigger another reaction. e. Because so many of its fissioning neutrons are captured by uranium-238 which then decays in other ways.
What is the ionosphere?
A) a layer of the atmosphere that is above the exosphere B) a layer of the atmosphere characterized by the presence of ozone C) a portion of the thermosphere in which the gas is ionized D) a portion of the troposphere in which ions are common
Pulling out of a dive, the pilot of an airplane guides his plane into a vertical circle with a radius of 600 m. At the bottom of the dive, the speed of the airplane is 150 m/s. What is the apparent weight of the 70.0-kg pilot at that point?
A) 3310 N B) 686 N C) 2630 N D) 489 N E) 1370 N
While examining the spectrum of a galaxy, you find all the hydrogen lines are shifted to longer wavelengths. This galaxy is
A) moving away from us. B) moving towards us. C) not forming new stars. D) expanding explosively. E) blueshifted.