Which of the following can never be negative?
A) acceleration of gravity
B) displacement
C) instantaneous speed
D) average velocity
E) instantaneous velocity
C
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Diagram below shows a hypothetical magnetic field in a certain region of empty space where the electric field is constant in time. 
Which of the fields are physically impossible and why?
A. This field violates the Ampere-Maxwell law. B. This field violates Gauss’s law for the magnetic field. C. The field violates both of the above laws. D. This field is physically possible.
It was the distribution of ________ that showed Harlow Shapley we were no where near the center of the Milky Way in the 1920s
A) planetary nebulae B) emission nebulae C) open clusters D) globular clusters E) supernova remnants
The number of impact craters on the slopes of Tharsis volcanoes suggests that they have been inactive
A) since Mars formed 4.6 billion years ago B) for at least a billion years C) for at least tens of millions of years D) only for the last few hundred years
The source of energy that keeps the Sun shining today is ________
A) gravitational contraction B) nuclear fusion C) chemical reactions D) nuclear fission