The density of the Universe is
a. equal to the critical density if the Universe is closed.
b. equal to the critical density if the Universe is flat.
c. greater than the critical density if the Universe is flat.
d. greater than the critical density if the Universe is open.
e. None of the other choices are correct.
b
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a. True b. False Indicate whether the statement is true or false
When astronomers use Hubble's law to measure the distance to a galaxy they have to measure the ________ of the galaxy.
A. mass B. recessional speed C. rotational speed D. luminosity
Three particles are placed in the xy plane. A 40-g particle is located at (3, 4) m, and a 50-g particle is positioned at (?2, ?6) m. Where must a 20-g particle be placed so that the center of mass of this three-particle system is located at the origin?
A. (?1, ?3) m B. (?1, 2) m C. (?1, 12) m D. (?1, 7) m E. (?1, 3) m
The motion of a piston in an automobile engine is nearly simple harmonic. If the 1-kg piston travels back and forth over a total distance of 15.6 cm, what is its maximum speed when the engine is running at 3 480 rpm?
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