archive the submit version

food_energy.tex

@@ -34,9 +34,9 @@
 
 % AJP header
 %When submitting the manuscript for review, do not include the author's name or institution
-%\author{Nathan T. Moore}
+\author{Nathan T. Moore}
-%\email{nmoore@winona.edu}
+\email{nmoore@winona.edu}
-%\affiliation{Physics, Winona State University, Winona, MN 55987}
+\affiliation{Physics, Winona State University, Winona, MN 55987}
 
 %IOP header
 %%\title[How many acres of potatoes does a society need?]{How many acres of potatoes does a society need?}
@@ -58,8 +58,7 @@ Science and Social Policy classes are full of bespoke units and involve many dif
 When the United States entered World War One one of the problems they faced was logistics.  How much food do you need to ship overseas to Europe to feed a million soldiers?  That early work in nutrition led to the $3000$ Calorie diet many people remember from secondary Health Education class.  A bit about ``Calorie'' (uppercase) vs ``calorie'' (lowercase) units you might remember: $1~Calorie = 1~kilocalorie~(kcal)$, and a dietitian might build a $3000 kcal$ diet for a 20 year old basketball player.  A \textit{calorie} is the amount of energy it takes  to heat a gram of water by a degree Celsius.  There are about $4.2$ Joules in a single calorie, and a Joule occurs all over introductory  physics.  If you need to buy a new home furnace, the sales brochure might advertise that it is capable of delivering $100,000$ BTU's of heat each hour.  What's a BTU? Heat a pound of water by $1^{\circ}F$.  Of course Heat Pumps are far more efficient than simply burning methane or propane, but they consume kilo-watt-hours (kWh) of electricity, not BTU's.  What's a kWh?  Run a $1000$ Watt toaster for an hour and you'll have pulled one kWh off the grid, it will cost you about $\$0.13$ in Minnesota.  If you decide to put solar panels in your backyard, they will probably collect about $10\%$ of the $3.5kWh$ the  the sun delivers to each square meter of your lawn (in Minnesota) each day.  
 
 As the previous paragraph illustrates, there are a frustratingly large number of different units in an ``Energy'' class.  At 
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 State, this 3 credit class fulfills a ``Science and Social Policy'' general education requirement and is taken by students from across the university.   Lots of college majors don't require a math class beyond algebra or introductory statistics and the population is largely math-averse. You could jokingly say that one of the main things students learn in the class is unit conversion, but it isn't far off.  Nearly every field finds energy a useful representation, and every profession has their own set of units and terminology most well suited for quick calculation.  Would a medical lab scientist talk about the fractional acre-foot of urine needed test kidney function?  No, but someone in the central valley of California would certainly care about the acre-feet of water necessary to grow almonds!  Does a gas station price their gasoline in dollars per kWh? Given the growing electrification of cars, they might soon.
 
 Everyone eats, maybe not $3000 kcals$ per day, but at least something every day.  When I teach our energy class,\cite{Energy_textbook,PFFP} 
@@ -74,8 +73,7 @@ To introduce Food Energy, I ask the students to work through a few questions:
 \includegraphics[width=\columnwidth]{at_the_buffet.jpg}
 \caption{
 A proto-college-student at 
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 China King Buffet, dreaming about visiting the steam tables every day. 
 }
 \label{buffet}
@@ -112,8 +110,7 @@ In medicine, these slopes are effectively equivalent to ``Metabolic Equivalent o
 
 \subsection{Burning off food energy}
 Imagine that after eating a $600kcal$ bacon-maple long-john (donut), you decide to go for a hike to ``work off'' the Calories.  
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 State  is in a river valley bounded by $200m$ tall bluffs.  How high up the bluff would you have to hike to burn off the donut?  
 Useful information: human muscle is about $1/3$ efficient, and on Earth's surface, gravitational energy has a slope of about $10~\frac{Joules}{kg\cdot m}$.