Olbers' paradox asks
A. Why isn't the night sky bright as day?
B. How can the Universe be younger than some of the stars in it?
C. If dark matter is dark, how can we ever see it?
D. Which is the simplest cosmological model?
Answer: A
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A figure skater rotating at 5.00 rad/s with arms extended has a moment of inertia of 2.25 kg • m2. If the arms are pulled in so the moment of inertia decreases to 1.80 kg • m2, what is the final angular speed?
A) 2.25 rad/s B) 4.60 rad/s C) 6.25 rad/s D) 1.76 rad/s E) 0.810 rad/s
An uncharged metal sphere is placed on an insulating puck on a frictionless table. While being held parallel to the table, a rod with a charge q is brought close to the sphere, but does not touch it. As the rod is brought in, the sphere
a. remains at rest. b. moves toward the rod. c. moves away from the rod. d. moves perpendicular to the velocity vector of the rod. e. moves upward off the puck.
According to the principle of relativity, an observer who has no communication with the world outside of her laboratory will be unable to detect
A) her laboratory's acceleration. B) her laboratory's velocity. C) Both of the above. D) gravity. E) All of the above.
A softball player determines her pitching speed by throwing a ball horizontally from an elevation of 5 m above the ground. The ball lands 20 m downrange. What is her pitching speed?
A) 5 m/s B) 10 m/s C) 20 m/s D) 25 m/s E) none of the above