This graph shows the frequency of impacts on Earth by objects of various sizes. According to this graph, objects large enough to cause a mass extinction hit Earth
A) about once every 50 million years.
B) about once every 1,000 years.
C) about once in Earth's history.
D) about once every 500 million years.
A) about once every 50 million years.
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The night sky is dark because the universe is not infinitely old
Indicate whether the statement is true or false
A charge of -4.00 nC is located at (0, 1.00) m. What is the x component of the electric field due to the charge at (4.00, -2.00) m?
1.1.15 N/C 2.-0.864 N/C 3.1.44 N/C 4.-1.15 N/C 5.0.864 N/C
Newton's Second Law in 1 Dimension: A 40-kg crate is being lowered with a downward acceleration is 2.0 m/s2 by means of a rope.(a) What is the magnitude of the force exerted by the rope on the crate?(b) What would be the magnitude of the force exerted by the rope if the crate were being raised with an acceleration of 2.0 m/s2?
Fill in the blank(s) with the appropriate word(s).
You discover a binary star system in which one star is a 15 MSun main-sequence star and the other is a 10 MSun giant. How do we think that a star system such as this might have come to exist?
A) The giant must once have been the more massive star, but it is now less massive because it transferred some of its mass to its companion. B) Although both stars probably formed from the same clump of gas, the more massive one must have had its birth slowed so that it became a main-sequence stars millions of years later than its less massive companion. C) The two stars probably were once separate, but became a binary when a close encounter allowed their mutual gravity to pull them together. D) The two stars are simply evolving normally and independently, and one has become a giant before the other.