The Doppler effect is observed only when
a. the source of a wave moves toward a stationary observer.
b. there is relative motion between the source of a wave and an observer.
c. an observer moves toward the stationary source of a wave.
d. both the source of a wave and an observer are moving toward each other.
b
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How does the hypothesis of inflation account for the existence of the "seeds" of density from which galaxies and other large structures formed?
A) Inflation would have caused random, microscopic quantum fluctuations to grow so large in size that they became the seeds of structure. B) Inflation predicts that gravity would have been very strong and thereby would have concentrated mass into seeds. C) Inflation tells us that the universe should have a "flat" overall geometry, and this led to the flat disks of galaxies. D) Inflation predicts that temperatures and densities should have become nearly equal throughout the universe.
A uniform thin wire has a length 
and is bent into a semicircular arc of radius R. If the wire starts at (x, y) = (R, 0) and curves counterclockwise to (x, y) = (?R, 0), what is the y coordinate of its center of mass?
What will be an ideal response?
If - = and A – B = C, then the vectors and are oriented perpendicular relative to one other
Indicate whether the statement is true or false
A constant-volume gas thermometer has a pressure of 2.00 atm at 100°C. What would its pressure be at 0°C?
A. 0.732 atm B. 1.46 atm C. 1.24 atm D. 1.37 atm E. More information is needed to find the answer.