What is the lifetime of a 10-solar-mass star on the main sequence?
a. 3.2 × 10^7 years
b. 320 years
c. 3.2 × 10^12 years
d. 1× 10^9 years
e. 1 × 10^11 years
Answer: a. 3.2 × 10^7 years
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A waterfall is 70 m high. What is the increase in water temperature at the bottom of the falls if all the initial potential energy goes into heating the water? (g = 9.8 m/s2, cw = 4186 J/kg•°C)
a. 0.16°C c. 0.69°C b. 0.34°C d. 1.04°C
The half-lives of cobalt-60 and strontium-90 are 5.3 years and 28 years respectively. Suppose that samples of cobalt-60 and strontium-90 are such that they initially have the same activity
What will be true of the numbers of cobalt-60 and strontium-90 nuclei in these samples? A) There will be more strontium-90 than cobalt-60 nuclei. B) There will be equal numbers of cobalt-60 and strontium-90 nuclei. C) There will be more cobalt-60 than strontium-90 nuclei. D) It is not possible to compare numbers of nuclei without knowing the masses of the samples.
Covalent bonding is caused by
A) the sharing of electrons between atoms. B) the transfer of electrons between atoms. C) unequal charge distributions around neutral molecules. D) atoms bonding to hydrogen molecules. E) atoms bonding to oxygen molecules.
Visible, luminous matter (such as the stars within galaxies) amounts to what percentage of the critical density (the density of mass-energy needed to make the geometry of the universe flat)?
A) 25 percent B) 50 percent C) less than 1 percent D) 10 percent