The escape velocity at the event horizon around a black hole is
a. smaller than the speed of light.
b. equal to the speed of light.
c. much larger than the speed of light.
d. irrelevant since nothing (including light) can escape from a black hole.
B
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Greenhouse gases in the atmosphere, such as carbon dioxide and water vapor, make Earth warmer than it would be otherwise because these gases __________.
a. form clouds that emit thermal radiation b. absorb infrared light emitted by the surface c. reflect visible light coming from the Sun d. absorb visible light coming from the Sun
According to relativity theory, you can experience a longer youth when you
A) are near a black hole. B) are near a very large gravitational field. C) travel at nearly the speed of light. D) all of the above E) none of the above
A mass on a spring undergoes SHM. When the mass is at maximum displacement from equilibrium, its instantaneous acceleration
A) is a maximum. B) is less than maximum, but not zero. C) is zero. D) cannot be determined without mass information given. E) cannot be determined without spring constant information given.
One of the most efficient engines built so far has the following characteristics: The combustion chamber temperature is 1900°C,
the exhaust temperature = 430°C, 7.0 × 109 cal of fuel produces 1.4 × 1010 J of work in one hour. (1 cal = 4.186 J) (a) What is the actual efficiency of this engine? (b) What is the power output of this engine? (c) What would be the maximum possible efficiency for an engine using the same temperature extremes?