What is a CCD, and how does it work? Why is it replacing film?
What will be an ideal response?
A charge coupled device consists of a grid of thousands of light-sensitive pixels that build up a digital image that can be stored on computer as light strikes it. It is digital, so it can be placed directly on magnetic tape or disks, or sent over a computer network. CCDs are also much more sensitive to fainter objects than are the fastest photo films.
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Suppose that, for some unknown reason, the core of the Sun suddenly became hotter. Which of the following best describes what would happen?
A) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and turn the Sun into a giant star. B) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal. C) Higher temperature would cause the rate of fusion to fall, decreasing the internal pressure and causing the core to collapse until the rate of fusion returned to normal. D) The higher temperature would not affect the fusion rate but would cause the core to expand and cool until the temperature returned to normal, with the core at a new, slightly larger size.
In the context of nuclear fusion in massive stars, hydrogen fusion can last 7 million years in a 25-solar-mass star, but that same star will fuse its oxygen in six months and its silicon in just one day
Indicate whether the statement is true or false
Is a fuel-cell vehicle properly described as a "heat engine"?
A) Yes, because it uses thermal energy to produce electricity. B) Yes, because it uses chemical energy to create electric energy. C) Yes, because it uses thermal energy to do work. D) No, because it converts chemical energy directly to electric energy. E) No, because it converts electric energy directly into chemical energy.
A driver in a 1000kg car traveling at 24m/s slams on the brakes and skids to a stop. If the coefficient of friction between the tires and the level road is 0.80, how long will the skid marks be?
A) 30 m B) 34 m C) 46 m D) 37 m