If you look for word problems about exponential growth or decay, in text books or on the internet, certain settings arise again and again:

1. bank accounts,
2. populations of animals, people or bacteria, and
3. temperature changes, as when something is taken from an oven or a refrigerator and allowed to come to room temperature.

I'd like to find more varied settings for exponential functions, including (it is hoped) some that are concave up or down, approaching an asymptote as x goes to positive or negative infinity.

If you look for word problems about exponential growth or decay, in text books or on the internet, certain settings arise again and again:

1. bank accounts,
2. populations of animals, people or bacteria, and
3. temperature changes, as when something is taken from an oven or a refrigerator and allowed to come to room temperature.

I'd like to find more varied settings for exponential functions, including (it is hoped) some that are concave up or down, and for each of those some that are increasing and some that are decreasing.