When is a rock considered an ore?
-when it occurs in sufficient amounts to be used to build roads and buildings
-only when it contains lead
-when it contains at least one metallic mineral in sufficient amounts to be extracted profitably
-only when it contains iron
-when it contains fluorite or sulfur minerals in sufficient amounts to be extracted profitably
when it contains at least one metallic mineral in sufficient amounts to be extracted profitably
when it contains fluorite or sulfur minerals in sufficient amounts to be extracted profitably
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The gain in speed each second for a freely-falling object is about
A) 0 m/s. B) 5 m/s. C) 10 m/s. D) 20 m/s. E) depends on the initial speed.
A square loop of wire has a current going around it. The magnetic field from the current on each side of the loop results in a magnetic force on the wire on the opposite side. Each resulting magnetic force on the opposite side wire
a. pushes inward on the loop. b. is actually zero since a current cannot push on itself. c. depends on whether the current is clockwise of counterclockwise. d. pushes outward on the loop.
A ball is thrown straight up. At what point does the ball have the most energy?
(a) At the highest point of its path. (b) When it is first thrown. (c) Just before it hits the ground. (d) When the ball is halfway to the highest point of its path. (e) Everywhere; the energy of the ball is the same at all of these points.
A charged particle moves with its velocity perpendicular to a magnetic field. The field acts to change the particle's
A) mass. B) magnitude of momentum. C) velocity. D) energy. E) charge.