What evidence leads astronomers to conclude that most of the Milky Way's mass consists of a mysterious dark matter?
A) We observe many dark clouds of gas that block the light of stars behind them.
B) The galaxy's rotation indicates that it must contain much more matter than we can observe with our telescopes.
C) Observations indicate that most stars are dimmer than the Sun, so we say they are "dark."
D) Stars are separated from one another by vast distances, and therefore most places in the galaxy would be dark to our eyes.
B) The galaxy's rotation indicates that it must contain much more matter than we can observe with our telescopes.
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_______ has the most tightly bound nucleus
a. Uranium b. Iron c. Helium d. Hydrogen
Einstein's theory of relativity tells us that travelers who make a high-speed trip to a distant star and back will ________
A) never be able to make the trip within their lifetimes B) age less than people who stay behind on Earth C) age more than people who stay behind on Earth D) have more fun than people who stay behind on Earth
Polarization: As shown in the figure, the orientation of the transmission axis for each of three ideal polarizing sheets is labeled relative to the vertical direction. A beam of light, polarized in the vertical direction, is incident on the first polarizer with an intensity of 1.00 kW/m2. What is the intensity of the beam after it has passed through the three polarizing sheets when ?1 = 30°, ?2 = 30°, and ?3= 60°?
A. 141 W/m2 B. 316 W/m2 C. 433 W/m2 D. 563 W/m2 E. 188 W/m2
A stonecutter's chisel has an edge area of 0.7 cm2 . If the chisel is struck with a force of 42 N, what is the pressure exerted on the stone?
a. 600 N/m2 b. 30,000 N/m2 c. 300,000 N/m2 d. 600,000 N/m2 e. 6000 N/m2