Nebula that tend to be reddish in color are the
A) emission nebula.
B) reflection nebula.
C) dark nebula.
D) magenta nebula.
Answer: A
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Two blocks of masses 20 kg and 9.0 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 9.0-kg mass is another light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.80 m/s2, what is the tension in the second string attached to the 9.0-kg mass?
a. 23 N b. 14 N c. 16 N d. 7.2 N e. 25 N
What is the image distance of an object 1.85 m in front of a converging lens of focal length 26.3 cm?
a. + 23.0 cm b. –1.99 cm c. + 30.6 cm d. + 159 cm e. + 4.80 cm
Which method of fueling your car is likely to be more energy efficient, and why: gasoline used in a standard car engine or electricity taken from a coal-fueled generating plant and stored in lightweight car batteries? Assume that the batteries
convert electricity to work at 100% efficiency, and that electricity is transported from the power plant to the car at 100% efficiency. A) Gasoline used in a standard car engine, because a car engine's fuel burns hotter and more efficiently than does the coal in a coal-fired power plant. B) Electricity from a coal-fired generating plant, because a car engine is a heat engine, and must follow the second law of thermodynamics, whereas a coal-fired generating plant is not. C) Gasoline used in a standard car engine, because a car engine burns its fuel directly in the automobile rather than miles away at the power plant. D) Electricity from a coal-fired generating plant, because such a plant runs at higher energy-efficiency than does a car engine. E) It wouldn't make any difference, because both the car engine and the generating plant are heat engines and are thus subject to the second law of thermodynamics.
The ratio of the density of a material to the density of water is
a. the mass density. b. the weight density. c. the specific gravity. d. the buoyant force. e. none of the above.