After seven half-lives have elapsed, what fraction of the original amount of radionuclide remains?
a. 1/7
b. 1/14
c. 1/128
d. None of these
c
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Though Titan has a small mass , it is able to retain an atmosphere because it
a. is very cold. b. is very hot c. has an iron surface. d. attracts gas from the solar wind.
An auto is moving at a steady 50 mph up a long straight [constant "slope"] incline. While it is on this incline,
A) its acceleration is zero but its velocity is not zero. B) its velocity and acceleration are both zero. C) its velocity is zero but its acceleration is not zero [i.e., it does have an acceleration]. D) neither its velocity nor its acceleration are zero. E) it has the heebie-jeebies.
A sphere made of a radioactive isotope initially has a mass of 6.88 kg. The half-life of this isotope is 1.34 h, and it decays by ?- emission. At the end of 2.68 h, what is the mass of this sphere?
A) 1.72 kg B) 2.53 kg C) 3.44 kg D) 6.88 kg
From the fact that virtually every galaxy is moving away from us and more distant galaxies are moving away from us at a faster rate than closer ones, we conclude that
A) the Milky Way Galaxy is expanding. B) we are located at the center of the universe. C) even nearby galaxies will eventually be moving faster than the speed of light. D) the universe is expanding. E) the universe is shrinking.