Thinking Like an Engineer: An Active Learning Approach (4th Edition)
4th Edition
ISBN: 9780134639673
Author: Elizabeth A. Stephan, David R. Bowman, William J. Park, Benjamin L. Sill, Matthew W. Ohland
Publisher: PEARSON
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Textbook Question
Chapter 12, Problem 17ICA
The total quantity (mass) of a radioactive substance decreases (decays) with time as
Where
t = time [days]
r = time constant
m0 = initial mass (at t=0)
m = mass at time t [mg]
A few milligrams each of three different isotopes of uranium were assayed for isotopic composition over a period of several days to determine the decay rate of each. The data were graphed and a mathematical model derived to describe the decay of each isotope.
- a. What are the units of T if time is measured in days?
- b. What is the initial amount of each isotope at t = 0?
- c. When will 1 milligram of the original isotope remain in each sample?
- d. Four isotopes of uranium are shown in the following table with their half-lives. Which isotope most likely matches each of the three samples? Note that one isotope does not have a match on the graph.
| Isotope | Half-life [days] |
| 230U | 20.8 |
| 231U | 4.2 |
| 237U | 6.75 |
| 240U | 0.59 |
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Chapter 12 Solutions
Thinking Like an Engineer: An Active Learning Approach (4th Edition)
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