Orthoclase and plagioclase are the two main types of
a. silica.
b. feldspars.
c. calcite.
d. sulfides.
b
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If you rub two transparency sheets with tissue and then hold the two transparency sheets at rest a short distance apart, they will then exert
A) a repulsive electric force on each other, but no magnetic force. B) a repulsive magnetic force on each other, but no electric force. C) an attractive electric force on each other, but no magnetic force. D) an attractive magnetic force on each other, but no electric force. E) no electric or magnetic forces on each other.
Given the observed average distance between galaxies today, which statement is true?
A) The faster the past expansion rate, the younger the age of the universe. B) The faster the past expansion rate, the older the age of the universe. C) The age of the universe depends only on the average distance between galaxies, not on the rate of expansion.
A star enters the main sequence when ________.
A. it forms planets B. nuclear fuel in its core can supply enough energy to stop its collapse C. it collapses, and its envelope becomes degenerate D. it stops fusing nuclear fuel in its core and starts to expand
All elements heavier than iron are made during supernova explosions
Indicate whether the statement is true or false