A star's color is related to its surface temperature because
A) stars emit thermal radiation.
B) the colors of stars depend mainly on the emission lines in the spectra.
C) stars have absorption lines in their spectra.
D) the color of a star depends on its mass, and mass is related to surface temperature.
A) stars emit thermal radiation.
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A radioisotope has a half-life of ? at a temperature of 150 K. If its temperature is increased to 300 K, what will its half-life be?
A) 4? B) 2 ? C) ? D) ?/2 E) ?/4
Evidence that there is a considerable amount of water frozen under the surface of Mars is provided by all of the following except
A. satellite measurements of water in the polar caps. B. discovery by the Mars rovers of chemicals in surface rocks formed in the presence of large amounts of water. C. squishy-looking flow patterns around crater impact sites. D. features resembling channels cut by flowing water. E. periodic eruptions of geysers when subsurface ice is melted by volcanic activity.
A car's initial velocity is 50.0 km/h in the direction 60.0° north of east, and its final velocity is 70.0 km/h in the direction 40.0° south of east. If the time period for this journey is 30.0 minutes, what is the magnitude of the car's average acceleration?
a. 186 km/h/h b. 240 km/h/h c. 92.8 km/h/h d. 3.94 km/h/h
A diverging lens will be prescribed by the eye doctor to correct which of the following?
a. myopia b. presbyopia c. hyperopia d. astigmatism