How did astronomers discover the relationship between spectral type and mass for main sequence stars?
A) by measuring the masses and spectral types of main-sequence stars in binary systems
B) by using computer models of hydrogen fusion and stellar structure
C) by measuring stellar radii with powerful telescopes
D) by comparing stars with the same spectral type but different luminosities
A) by measuring the masses and spectral types of main-sequence stars in binary systems
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Select the best filter for a cobalt x-ray tube that will reduce the intensity of the K? line and transmit the cobalt K? line.
(a) What are the wavelength of the cobalt K? and K? line? (b) What is your selected filter material? (c) What is the wavelength of the K absorption edge of your selected filter material?
Which of the following best describes the sizes of atoms?
A) Atoms are so small that millions of them could fit across the period at the end of this sentence. B) Atoms are too small to see by eye, but can be seen with a handheld magnifying glass. C) Most atoms are about a millionth of a meter (1 micrometer) in diameter. D) Atoms are roughly the same size as typical bacteria.
Columbus was the first person to discover that Earth is round
Indicate whether the statement is true or false
Uniform Circular Motion: In order to simulate weightlessness for astronauts in training, they are flown in a vertical circle. If the passengers are to experience weightlessness, how fast should an airplane be moving at the top of a vertical circle with a radius of 2.5 km?
A. 79 m/s B. 310 m/s C. 260 m/s D. 160 m/s E. 510 m/s