1. Laws of Growth and Decay!!!
Whoa… it’s
Extra Practice for
Laws of Growth and Decay!!!
Rita Korsunsky

2. Pythagoras the Platypus drank a cup of hot chocolate in the 14º weather to keep himself warm. At first, the 81º hot chocolate burned his tongue, but after 6 minutes, it cooled down to 63º and Pythagoras was able to drink it.
a) The temperature is changing at a rate directly proportional to the difference between the temperature of the hot chocolate and the temperature of the surrounding medium. What is the equation of the drink cooling?

3. Pythagoras the Platypus drank a cup of hot chocolate in the 14º weather to keep himself warm. At first, the 81º hot chocolate burned his tongue, but after 6 minutes, it cooled down to 63º and Pythagoras was able to drink it.
b) After waiting 15 minutes for the shuttle bus, what is the temperature of his hot chocolate?
From part (a), the equation of the temperature is…
Plug in t=15
After 15 minutes, the temperature of the hot chocolate is º

4. After descending from Mars' atmosphere, the rover Nemo reaches a temperature of 375°F.  The unit has cooled to 150°F after waiting 30 minutes in 50° wind gusts.  Use Newton's Law of Cooling to find out how many more minutes Nemo must wait until it reaches 100°F?

5. After descending from Mars' atmosphere, the rover Nemo reaches a temperature of 375°F.  The unit has cooled to 150°F after waiting 30 minutes in 50° wind gusts.  Use Newton's Law of Cooling to find out how many more minutes Nemo must wait until it reaches 100°F?
Plug in y=100°F
It must wait more minutes.
Nemo has already waited 30 minutes, so…

6. (a) Find an expression for the number of cells after t hours.
A cell of a particular bacterium in a nutrient-broth medium divides into two cells every 20 minutes. The rate of growth is directly proportional to the number of cells present. The initial population of the culture is 60 cells.
(a) Find an expression for the number of cells after t hours.
(b) Find the number of cells after 8 hours.
(c) Find the rate of growth after 8 hours.
(d) When will the population reach 20,000 cells?
=20 min
Divides into 2

7. A cell of a particular bacterium in a nutrient-broth medium divides into two cells every 20 minutes. The rate of growth is directly proportional to the number of cells present. The initial population of the culture is 60 cells.
(a) Find an expression for the number of cells after t hours.
(b) Find the number of cells after 8 hours.
(c) Find the rate of growth after 8 hours.
(d) When will the population reach 20,000 cells?
(b)
From part (a)
(c)

8. Awesome! Thanks for helping me solve this problem!
A cell of a particular bacterium in a nutrient-broth medium divides into two cells every 20 minutes. The rate of growth is directly proportional to the number of cells present. The initial population of the culture is 60 cells.
(a) Find an expression for the number of cells after t hours.
(b) Find the number of cells after 8 hours.
(c) Find the rate of growth after 8 hours.
(d) When will the population reach 20,000 cells?
Awesome! Thanks for helping me solve this problem!

9. Wow.
It’s OVER.
Good bye.