Chapter 1, Problem 17DE

Forensics At 8:30 A.M., a coroner went to the home of a person who had died during the night. In order to estimate the time of death, the coroner took the person’s temperature twice. At 9:00 A.M. the temperature was 85.7F, and at 11:00 A.M. the temperature was 82.8F. From these two temperatures, the coroner was able to determine that the time elapsed since death and the body temperature were related by the formula t=10lnT7098.670 where t is the time in hours elapsed since the person died and T is the temperature (in degrees Fahrenheit) of the person’s body. (This formula comes from a general cooling principle called Newton’s Law of Cooling. It uses the assumptions that the person had a normal body temperature of 98.6F at death and that the room temperature was a constant 70F.) Use the formula to estimate the time of death of the person.

Flood Control A river is 8 feet above its flood stage. The water is receding at a rate of 3 inches per hour. Write a mathematical model that shows the number of feet above flood stage after t hours. Assuming the water continually recedes at this rate, when will the river be 1 foot above its flood stage?