What is the main reason mountaintops are so cold?
A) The air is thinner at higher altitudes.
B) Mountaintops are above much of the greenhouse gas in the atmosphere.
C) The winds are stronger at higher altitudes.
D) There is more water vapor at higher altitudes, causing there to be more snow.
E) All of the above are true.
B
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Power: A series RLC circuit has a 100-? resistor, 2.0-mH inductor and a 4.0-?F capacitor connected across a 120-V rms ac source at 1000/? Hz. What is the power factor of this circuit?
A. 0.54 B. 0.64 C. 0.74 D. 0.84 E. 0.94
How do velocity and acceleration differ?
a. They are the same thing. b. Velocity has direction but acceleration does not. c. Acceleration is the rate of change of velocity, while velocity is the rate of change of displacement. d. Average acceleration can be measured but average velocity cannot. e. Velocity is the rate at which acceleration changes.
What can be said with certainty about a red star and a blue star?
A) The red star is closer to Earth than the blue star. B) The red star is more massive than the blue star. C) The blue star has a greater proper motion than the red star. D) The blue star is hotter than the red star. E) The red star has a greater radial velocity than the blue star.
Frank says that if you release the string when swinging a ball in a horizontal circle, the ball flies out in the radial direction defined by the string at the instant you release the ball. John says that it flies out along a tangent line perpendicular to the string, and that it then drops straight down to the ground. Which one, if either, is correct?
a. Frank, because the centrifugal force is no longer counteracted by the string. b. Frank, because balls naturally fly straight out. c. John, because there is no centrifugal force. d. John, because balls fall straight down when released. e. Neither, because although there is no centrifugal force, and the ball's velocity is tangent to the circle at the instant of release, the ball then follows a parabolic trajectory.