1. A certain radioactive material follows the law of exponential growth. If between noon and 2 pm the population triples, at what time should the population become 100 times what it was at noon? 2. A thermometer is taken from an inside room to the outside ,where the air temperature is 5° F. After 1 minute the thermometer reads 55° F, and after 5 minutes it reads 30° F, what is the initial temperature of the inside room?

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Applications of differential equations

1. A certain radioactive material follows the law of exponential growth. If between noon and 2 pm the population triples, at what time should the
population become 100 times what it was at noon?
2. A thermometer is taken from an inside room to the outside ,where the air temperature is 5° F. After 1 minute the thermometer reads 55° F, and after 5
minutes it reads 30° F, what is the initial temperature of the inside room?
Transcribed Image Text:1. A certain radioactive material follows the law of exponential growth. If between noon and 2 pm the population triples, at what time should the population become 100 times what it was at noon? 2. A thermometer is taken from an inside room to the outside ,where the air temperature is 5° F. After 1 minute the thermometer reads 55° F, and after 5 minutes it reads 30° F, what is the initial temperature of the inside room?
3. A small metal bar, whose initial temperature was 20° C, is dropped into a large container of bowling water. How long will it take the bar to reach 90°C if
it is known that its temperature increase to 22°C in 1 second?
4. A tank initially holds 80 gal of a brine solution containing 1/8 Ib of salt per gallon. At t = 0, another brine solution containing 1 lb of salt per gallon is
poured into the tank at the rate of 4 gal/min, while the well-stirred mixture leaves the tank at the rate of 8 gal/min. Find the amount of salt in the tank
when the tank contains exactly 40 gal of solution
Transcribed Image Text:3. A small metal bar, whose initial temperature was 20° C, is dropped into a large container of bowling water. How long will it take the bar to reach 90°C if it is known that its temperature increase to 22°C in 1 second? 4. A tank initially holds 80 gal of a brine solution containing 1/8 Ib of salt per gallon. At t = 0, another brine solution containing 1 lb of salt per gallon is poured into the tank at the rate of 4 gal/min, while the well-stirred mixture leaves the tank at the rate of 8 gal/min. Find the amount of salt in the tank when the tank contains exactly 40 gal of solution
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