Which of the following is required for helium fusion as compared to hydrogen fusion?
A) much higher temperature
B) much higher density
C) a star of much greater mass
D) a star that is much older in age
A) much higher temperature
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Another name for cyanobacteria, the earliest evidence of ancient life, is
a. blue-green algae. b. amber. c. foraminifera. d. coal.
A figure skater rotating at 5.00 rad/s with arms extended has a moment of inertia of 2.25 kg?m2. If the arms are pulled in so the moment of inertia decreases to 1.80 kg?m2, what is the final angular speed?
A) 2.25 rad/s B) 4.60 rad/s C) 6.25 rad/s D) 1.76 rad/s E) 0.81 rad/s
A thin lens of focal length 20 cm is placed in contact with a 40-diopter thin lens. What is the power of the combined lenses?
a. 1/4 diopter b. 35.0 diopters c. 45.0 diopters d. 80 diopters e. 4 diopters
What was one obstacle Newton encountered in developing his theory of universal gravitation from his observation of heavenly bodies?
a. He had to prove that Earth was nearly spherical. b. He had to figure out why the Moon doesn't fall down. c. He had to spend many years observing the movement of the planets. d. He had to prove that the mass of the Earth acts as if it was concentrated at the planet's center. e. He had to prove the inverse-square law.