What kind of object do we think lies in the center of the Milky Way Galaxy?
A) a 3- to 4-million-solar-mass black hole
B) a gigantic X-ray binary system
C) a dense cluster of young, hot stars
D) an enormous collection of dark matter, which explains why we detect no light at all from the galactic center
A
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The last step in cosmic evolution is:
A) particulate evolution. B) stellar evolution. C) chemical evolution. D) biological evolution. E) cultural evolution.
Suppose you electrically charge a transparency by rubbing it, and then hang the transparency, at rest, by a string in the center of a room. Except for the transparency and string, the room is totally evacuated of all matter
Neglecting any influences from outside the room, what kinds of fields would then be found at places inside the room but away from the transparency--for instance, at a point near a corner of the room? A) an electric field only B) a magnetic field only C) Both an electric and magnetic field D) No fields at all, because the transparency would create electromagnetic fields only within the transparency itself E) No fields at all, because there is nothing [no material object] at such a point
If a metallic wire of cross-sectional area 4.0 × 10^?6 m2 carries a current of 7.0 A and has a mobile charge density of 4.24 × 10^28 carriers/m3, what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 × 10^?19 C)
a. 1.8E+3 m/s b. 1.7E+3 m/s c. 4.1E–4 m/s d. 2.6E–4 m/s e. 7.0E–6 m/s
A human, running up stairs, can briefly use power of approximately
A. 0.01 horsepower B. 0.1 horsepower C. 0.2 horsepower D. 1 horsepower