The number of _______________ on the Sun varies over an 11-year cycle
a. sunspots
b. rays
c. canals
d. valleys
a
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An object is placed in front of a convex mirror at a distance larger than twice the focal length of the mirror. The image will appear
A) in front of the mirror. B) inverted and reduced. C) inverted and enlarged. D) upright and reduced. E) upright and enlarged.
According to current evidence, Pluto is best explained as ______.
Fill in the blank(s) with the appropriate word(s).
Current evidence suggests the universe will continue to expand forever, but some people would prefer if we lived in a recollapsing universe that would eventually stop expanding and start contracting. Based on current understanding, which of the following would have to be true for our universe to fit a recollapsing model?
A) Dark energy does not exist and there is much more matter than current evidence suggests. B) Dark energy is the dominant form of energy in the cosmos. C) The density of dark matter turns out to be greater than the density of dark energy. D) The total density of matter equals the critical density.
The vector sum of three co-planar forces
a. must be zero. b. must be perpendicular to one of the three. c. must be parallel to one of the three. d. must be perpendicular to the plane. e. may have any direction in the plane.