Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant?
A) spectral type M1, luminosity class V
B) spectral type O9, luminosity class I
C) spectral type G2, luminosity class V
D) spectral type M2, luminosity class I
D
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A hockey puck traveling at speed v on essentially frictionless ice collides with one end of a straight stick lying flat on the ice and sticks to that end. In this collision
a. momentum is conserved. b. angular momentum is conserved. c. energy is conserved. d. all of the above are conserved. e. only momentum and angular momentum are conserved.
Carly places one end of a steel bar in a Bunsen flame and the other end in an ice cube. By what factor is the rate of heat flow changed when the bar's cross-sectional area is tripled?
a. 0.33 c. 3.0 b. 1/9 d. 9.0
An astronaut on another planet drops a 1-kg rock from rest. The astronaut notices that the rock falls 2 meters straight down in one second. On this planet, how much does the rock weigh?
A) 1 N B) 4 N C) 5 N D) 10 N
A wire of resistivity ? must be replaced in a circuit by a wire four times as long. If, however, the total resistance is to remain as before, the diameter of the new wire must
A) remain unchanged. B) be two times smaller. C) be four times smaller. D) be two times larger. E) be four times larger.