During the first moments of the big bang when elements could be created, nuclear fusion reactions made few heavy elements because
a. all heavy nuclei are unstable.
b. no stable nuclei exist with masses of 5 or 8 hydrogen masses.
c. the helium nucleus is unstable.
d. the temperature and density were too low.
e. no nuclei heavier than helium could form since there weren't any electrons formed.
B
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The period-luminosity relation is useful in determining
a. the mass of a star for which the distance is known. b. the temperature of a star for which we know the luminosity. c. the radius of the bulge of our galaxy. d. the distance to globular clusters that contain Cepheid variables. e. the mass of the Milky Way galaxy.
A 1200-kg car is being raised with a constant acceleration of 2.53 m/s2 by a crane, using a 20-m long steel cable that is 1.5 cm in diameter. Young's modulus for steel is 2.0 × 1011 N/m2
What is the change in length of the cable caused by lifting the car? A) 8.4 mm B) 8.4 cm C) 4.9 mm D) 4.9 cm E) 4.9 m
Heat is
A) temperature. B) thermal energy. C) thermal energy flowing from hot to cold. D) radiant energy.
A particle confined to motion along the x axis moves with constant acceleration from x = 2.0 m to x = 8.0 m during a 2.5-s time interval. The velocity of the particle at x = 8.0 m is 2.8 m/s. What is the acceleration during this time interval?
a. 0.48 m/s2 b. 0.32 m/s2 c. 0.64 m/s2 d. 0.80 m/s2 e. 0.57 m/s2