The radius of the earth is R. At what distance above the earth's surface will the free-fall acceleration be 4.9 m/s2?
A) 0.41 R
B) 0.50 R
C) 1.00 R
D) 1.41 R
E) 0.25 R
A
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Microfossils found in northwestern Australia in 2011 appears to have used compounds based on which element for metabolism?
A) sulfur B) oxygen C) nitrogen D) carbon
Earth's magnetic field is not stable; throughout geologic time it has changed direction. This change is attributed to
A) changes in the direction of fluid flow in the molten outer core of Earth. B) magnetic pole reversals. C) fluctuations in the time / space continuum. D) changes in the direction of fluid flow in the molten inner core of Earth.
One of the lines of Hydrogen has a wavelength of 121.6 nm. If a cloud of Hydrogen gas is moving TOWARDS us at 200km/s, what will we detect?
a) An emission line in the cloud's spectrum with a wavelength shorter than 121.6 nm. b) An emission line in the cloud's spectrum with a wavelength longer than 121.6 nm. c) An emission line in the cloud's spectrum with a wavelength of exactly 121.6 nm. d) This cloud will not emit a spectrum at all. e) A continuous spectrum with an absorption line at exactly 121.6 nm.
Why have refrigerators been the focus of so much research in lowering energy use?
What will be an ideal response?