Why are Cepheid variables so important for measuring distances in astronomy?
A) They all have the same luminosity.
B) They all have the same period.
C) Their luminosity can be inferred from their period.
D) They are close enough to have a detectable parallax.
E) They are circumpolar like Polaris, the North Star.
C
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Two surveyors measure the distance across a river that they cannot cross. They drive two stakes into the ground and find that the distance between the stakes, the baseline, is 15 meters. They choose a pole as a landmark on the opposite side of the river. This forms a triangle, with the two stakes as two corners and the pole as the third corner. When sighting the pole from the two ends of the
baseline, the two angles formed on their side of the river are 82° and 67°. The distance from the baseline to the pole calculated using the triangulation method is approximately _____. A) 76 meters B) 83 meters C) 26 meters D) 43 meters
Which of the following studies is best suited to astronomical observations that fall into the category called time monitoring?
A) studying how a star's brightness varies over a period of 3 years B) studying how different planets differ in their surface compositions C) measuring the rotation rate of a distant star D) determining the age of the solar system
We know that Earth has water. However, according to our theory of solar system formation, the inner solar system was too hot for hydrogen compounds like water to condense. What do we conclude?
A) Water arrived on Earth at a time when it rained throughout the inner solar system. B) Earth's water likely was brought here by asteroids or comets that formed beyond the frost line. C) Our theory of solar system formation will need modification because it is unable to account for the existence of water on Earth. D) Earth's water probably originated through chemical reactions among the rock and metal of Earth's interior.
An 80-kg man is skating northward and happens to suddenly collide with a 20-kg boy who is ice skating toward the east
Immediately after the collision, the man and boy are seen to be moving together at 2.5 m/s in a direction 60° north of east. How fast was the boy moving just before the collision?