Protostars initially do not experience hydrogen fusion. How does their temperature increase?
A. fusion of hydrogen into helium
B. the light from nearby stars
C. energy from their magnetic fields
D. gravitational energy from infalling material
Answer: D
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Suppose that we connect two identical realistic batteries in parallel. The internal resistance of the combined set of batteries (considered as a unit) is
A. twice that of each individual battery. B. half that of each individual battery. C. the same as that of each individual battery.
In general, what is true of the alpha star in a constellation?
A) It is the easternmost star in the constellation. B) It is the brightest star in the constellation. C) It is the westernmost star in the constellation. D) It is the star that is closest to Earth. E) It is the reddest star in the constellation.
A policeman walks on his beat back and forth. His average speed is determined from
A. time divided by how far he ends up from the starting point. B. his velocity divided by the time. C. time divided by his total distance covered. D. his total distance covered divided by the time.
A 2.0-m straight wire carrying a current of 0.60 A is oriented parallel to a uniform magnetic field of 0.50 T. What is the magnitude of the magnetic force on it?
A) zero B) 0.15 N C) 0.30 N D) 0.60 N