The period-luminosity law of pulsating variable stars indicates that
A. the period of pulsation is independent of luminosity.
B. the more slowly a star pulsates, the more luminous it is.
C. the faster a star pulsates, the more luminous it is.
D. None of these choices is correct.
Answer: B
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Earth observes a rocket move away at 0.370c. The rocket is designed to launch a projectile at 0.505c relative to the rocket
(a) Fired straight ahead, what is the projectile speed observed from Earth? (b) Launched to the rear, what is the projectile speed observed from Earth?
What best explains the darkness of the rings beyond Saturn's?
A) Water ice reflects light poorly at the low temperatures beyond Saturn. B) Old, sooty debris and radiation darkening. C) Rocky debris doesn't reflect as well as water ice. D) They are pieces of captured comets. E) The sunlight is much fainter out there.
Jet planes operate by
A) rocket drive [i.e., ejecting heated rocket fuel rapidly out the back end of the engine]. B) ejecting ions out the back end of the engine. C) sucking in air, heating it , and allowing it to expand out the back end of the engine. D) sucking in air and blowing it rapidly out the back of the engine by means of propeller blades inside the engine. E) magic.
A high tide is occurring at Charleston, South Carolina (45°W, 64°N). Which listed longitude is experiencing a low tide occurring?
a. 135°E b. 65°E c. 45°E d. 45°W e. 145°W