What can we say about stars that contain relatively few amounts of heavy elements?
A.) They are younger than stars with more heavy elements.
B.) They are older than stars with more heavy elements.
C.) They are the same age as stars with more heavy elements.
D.) They are actually brown dwarfs.
E.) They are actually white dwarfs.
Ans: B.) They are older than stars with more heavy elements.
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In order to control a nuclear reactor, control rods can be pulled out of or pushed into the reactor core by remote control. These rods control the reactor by
a. slowing down the fast neutrons so the neutrons can be absorbed by 238U. b. speeding up slow neutrons so the neutrons can be absorbed by 238U. c. slowing down fast neutrons so they cannot initiate further fusion reactions in 235U. d. speeding up fast neutrons so they cannot initiate further fusion reactions in 235U. e. capturing thermal neutrons so they cannot initiate further fission reactions in 235U.
How is Titan, the moon of Saturn, similar to the Earth?
A) like the Earth, Titan has an atmosphere made mostly of molecular nitrogen B) Titan, like the Earth, has an internal magnetic field C) like the Earth, Titan has oceans of liquid water on its surface D) Titan is almost the same size as the Earth
Lillian pulls on a 10-kg wagon with a constant force of 30 N. What is the wagon's acceleration?
A) 0.3 m/s2 B) 3.0 m/s2 C) 10 m/s2 D) 30 m/s2 E) 300 m/s2
A child has a temperature of 101°F. If her total cross-sectional area is 2 m2, find the energy lost each second (in W) due to radiation, assuming the emissivity is 1 . (Assume the room temperature is 70°F.)
a. 217 b. 180 c. 90 d. 68 e. 850