What is a gluon?
a. A flavor of quark.
b. The most newly discovered lepton.
c. A combination of three complementary quarks.
d. A particle exchanged by quarks.
e. A particle exchanged by electrons to give electrical repulsion.
d
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A 200-kg spacecraft is launched to the Moon. After it has landed on the Moon, its mass is ________.
A. zero B. 200 kg C. about 1/6 its mass on Earth D. The answer depends on which side of the Moon the spacecraft landed on.
Oceans are about four times as deep as mountains are high. At the bottom of the ocean are
A) towering mountains, deep valleys, and deep trenches near the continental borders. B) thick layers of basaltic crust at mid-ocean ridges that gradually thin near deep ocean trenches. C) towering plutonic mountains created from volcanoes and fissures at oceanic ridge areas. D) all of these
Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?
A) still in the same place, below Polaris B) to the left of Polaris; that is, 90 degrees clockwise from its current position C) directly above Polaris D) to the right of Polaris; that is, 90 degrees counterclockwise from its current position
The type of EM waves used in radar is
a. ultraviolet b. infrared c. x ray d. microwave e. blackbody