Which of the following best describes convection?
A) Rocks sink in water.
B) Warm material expands and rises while cool material contracts and falls.
C) Warm material gets even warmer and cool material gets even cooler.
D) A liquid separates according to density, such as oil and water separating in a jar.
E) Bubbles of gas move upward through a liquid of the same temperature.
B) Warm material expands and rises while cool material contracts and falls.
You might also like to view...
A person throws three rocks off a cliff of height h at exactly the same speed 
, each time, but throwing rock A almost vertically upward, rock B horizontally, and rock C almost vertically downward (see the diagram below). 
Which rock hits the ground with the greatest speed? (Ignore air friction.) A. Rock A B. Rock B C. Rock C D. Rocks A and C hit with the same speed, faster than B. E. All three rocks hit with the same speed.
Answer the following statement(s) true (T) or false (F)
1. Suppose you are in a train traveling at one-half of the speed of light relative to the earth. Assuming that photons emitted by the train’s headlight travel at the speed of light relative to you, they would (according to the Galilean velocity transformation) travel at 1.5 times the speed of light relative to the earth. 2. Suppose you are in a spaceship traveling at twice the speed of light relative to the earth. Assuming that the Galilean transformation equations are true and the earth is approximately at rest relative to the ether, light from the ship’s taillight will never reach the ship’s bridge at its front end.
Magnetic Poles: If you were to cut a small permanent bar magnet in half,
A. one piece would be a magnetic north pole and the other piece would be a south pole. B. neither piece would be magnetic. C. each piece would in itself be a smaller bar magnet with both north and south poles. D. None of these statements is true.
The photons of blue light have:
A) more energy than the photons of red light. B) more energy than the photons of ultraviolet light. C) a lower frequency than the photons of red light. D) a longer wavelength than the photons of red light.