Which of the following statements about matter—antimatter engines is not true?
A) Matter—antimatter engines would be great in theory, but to date we have no evidence that antimatter even exists.
B) Matter—antimatter reactions represent the most efficient possible reactions in terms of energy release.
C) Spacecraft powered by matter—antimatter engines could probably reach speeds of more than half the speed of light.
D) One of the major challenges to developing matter—antimatter engines is finding a way to store antimatter after it is produced.
A) Matter—antimatter engines would be great in theory, but to date we have no evidence that antimatter even exists.
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The lobes of a radio galaxy can be as much as
A) dozens of light-years from the galaxy's nucleus. B) hundreds of light-years from the galaxy's nucleus. C) thousands of light-years from the galaxy's nucleus. D) millions of light-years from the galaxy's nucleus. E) billions of light-years from the galaxy's nucleus.
The Kelvin temperature of an ideal gas is doubled and the volume is halved. How is the pressure affected?
A. increases by a factor of 2 B. increases by a factor of 4 C. stays the same D. decreases by a factor of 2 E. decreases by a factor of 4
According to our present theory of solar system formation, which of the following lists the major ingredients of the solar nebula in order from the most abundant to the least abundant?
A) hydrogen and helium gas; rock; metal; hydrogen compounds B) hydrogen and helium gas; hydrogen compounds; rock; metal C) hydrogen, water, methane, helium D) hydrogen compounds; hydrogen and helium gas; metal; rock
An ice cube is floating in a glass of water with the water level just reaching the top of the glass. If the temperature in the surrounding area is above freezing, the ice cube will melt. When it does,
A. the water level in the glass will remain unchanged as the ice continues to melt. B. the water level in the glass will begin to go down. C. water will begin to spill over the top of the glass. D. it is impossible to tell what the water level will do from the information given.