An isolated object is initially spinning at a constant speed. Then, although no external forces act upon it, its rotational speed increases. This must be due to
A. a decrease in the moment of inertia.
B. an increase in the mass.
C. an increase in the moment of inertia.
D. an increase in the angular momentum.
E. impossible, angular momentum conservation is violated.
Answer: A
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Which of the following is a prime number?
A) 13 B) 21 C) 49 D) 15
____ is absorbed by ozone in Earth's atmosphere that is located between 20 km and 40 km above Earth's surface. Therefore, telescopes to observe this radiation must be placed in space
a. Infrared radiation b. Ultraviolet radiation c. Radio wave radiation d. X-ray radiation e. Visible light
Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4-solar-mass limit?
A) The upper limit to a white dwarf's mass is something we have learned from observations, but no one knows why this limit exists. B) Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4-solar-mass limit. C) White dwarfs get hotter with increasing mass, and above the 1.4-solar-mass limit they would be so hot that even their electrons would melt. D) White dwarfs are made only from stars that have masses less than the 1.4-solar-mass limit.
The graph represents the velocity of a car over time. Where the car ends up, relative to its starting point, can be found by
A. adding the slopes of each section of the graph.
B. adding area 1 to area 2.
C. subtracting area 2 from area 1.
D. subtracting area 1 from area 2.
