On average, how often do impacts large enough to produce mass extinction on the Earth occur?
A) once every century
B) once every million years
C) once in Earth's history
D) once every thousand years
E) once every hundred million years
E
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A straight 10-cm wire bent at its midpoint so as to form an angle of 90° carries a current of 10 A. It lies in the xy plane in a region where the magnetic field is in the positive z direction and has a constant magnitude of 3.0 mT. What is the magnitude of the magnetic force on this wire?
a. 3.2 mN b. 2.1 mN c. 5.3 mN d. 4.2 mN e. 6.0 mN
Suppose we imagine the Sun to be about the size of a grapefruit. Which of the following describes the size and distance of Earth on the same scale?
A) Earth is the size of a tip of a ballpoint pen about 1 meter away from the Sun. B) Earth is the size of a golf ball about 1 meter away from the Sun. C) Earth is the size of a tip of a ballpoint pen about 15 meters away from the Sun. D) Earth is the size of a golf ball about 15 meters away from the Sun. E) Earth is the size of a marble about 25 miles away from the Sun.
The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e); note that (a) represents the entire main sequence while (c) and (d) represent only small parts of the main sequence
Which group represents stars that are extremely bright and emit most of their radiation as ultraviolet light? A) a B) b C) c D) d E) e
Two electromagnetic have different frequencies but equal amplitudes. The one with higher frequency has the
A) greater energy. B) greater speed. C) longer wavelength. D) All of the above. E) None of the above.