What behavior do galactic rotation curves exhibit to suggest the existence of dark matter in an extended halo?
a. Small velocities are seen at large distances from the galactic center.
b. Small velocities are seen at distances close to the galactic center.
c. Large velocities are seen at large distances from the galactic center.
d. Large velocities are seen at distances close to the galactic center.
C
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In the context of a star's spectrum, which of the following statements is true of a giant star?
A) Hydrogen atoms in its atmosphere do not often collide with each other. B) Its atmosphere is very dense. C) Its spectrum has very broad spectral lines. D) Energy levels are not distorted when atoms in its atmosphere collide.
A jet plane travels around the world at 2 000 mi/hr (894 m/s). Two accurate atomic clocks measure the times of flight, one on board the plane and the second on Earth. If it takes 12 hours to complete the journey, what will the time difference (in ?s) be?
a. 0.75 b. 0.50 c. 0.25 d. 1.0 e. 0.19
The SI units of acceleration are
a. mi/h b. km/h c. m/s d. m/s2 e. none of the above
The ocean can be divided into several vertical layers—the surface zone, a transition zone, and the deep zone. As one descends to lower depths, water pressure ________ and temperature ________
A) increases; decreases B) decreases; increases C) increases; increases D) decreases; decreases