The half-life of cobalt-60 is 5.3 years, while that of strontium-90 is 28 years
Suppose that samples of cobalt-60 and strontium-90 are such that they initially have the same activity (number of decays per second). What is true about the initial numbers of cobalt-60 and strontium-90 nuclei in these samples?
A) There are equal numbers of cobalt-60 and strontium-90 nuclei.
B) There are more cobalt-60 than strontium-90 nuclei.
C) It is not possible to compare numbers of nuclei without knowing the masses of the samples.
D) There are more strontium-90 than cobalt-60 nuclei.
D
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The nuclear bulge of our galaxy
a. contains stars that are primarily population I stars. b. is primarily composed of gas and dust. c. contains stars primarily associated with the spherical component of our galaxy. d. contains stars primarily associated with the disk component of our galaxy. e. contains stars that are primarily population I stars, is primarily composed of gas and dust, and contains stars primarily associated with the disk component of our galaxy.
Each dot on this graph represents an individual Cepheid variable star. Which of the following is true for a Cepheid that is 10,000 times as luminous as the Sun?
A) It varies gradually in brightness, with a peak in brightness about every 30 days. B) It orbits the center of the galaxy about every 30 days. C) It orbits its binary companion about every 30 days. D) It undergoes a massive flare about every 30 days.
In the previous question, just before hitting the ground, what is the final speed of the heavy stone compared to the light one?
a) quarter as much b) half as much c) the same d) twice as much e) four times as much
A 0.600-mm diameter wire stretches 0.500% of its length when it is stretched with a tension of 20.0 N. What is the Young's modulus of this wire?
A) 5.66 × 1010 N/m2 B) 3.54 × 109 N/m2 C) 1.41 × 1010 N/m2 D) 6.43 × 109 N/m2 E) 2.78 × 109 N/m2