"Spurs" are probably the result of ____
a. self-sustaining star formation
b. spiral density waves
c. differential rotation
d. the central galactic bar
e. the short lifetime of O stars
a
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Which of the state vectors below is not physically equivalent to 
?
E. They are all equivalent.
Suppose one's hand exerts a force of 12 N upward on a book weighing 10 N. The reaction to the force of the hand on the book is a force of
A. 2 N exerted by the book on the hand. B. 10 N exerted by the Earth on the book. C. 10 N exerted by the book on the hand. D. 10 N exerted by the book on the Earth. E. 12 N exerted by the book on the hand.
Homogeneous mixtures are also called ______________
Fill in the blank(s) with correct word
The direction of a field line at a point in space shows the direction of the force that would act on a body placed at the point
Indicate whether the statement is true or false