In these parts, "Food Liar" is a well-liked pejorative for Food Lion,
a somewhat run-down grocery chain. Having somehow been placed on
their spamming list, I recently received a colorful chart, a matrix
of calories burned in 30 min for a variety of activities, vs weight.
I suggest these sorts of things as interesting and useful classroom
tools: real-world, relevant, and perhaps vaguely interesting to a
certain cross-section of students.
Aside from whether the chart is accurate as to calorie count (a more
complex question), one can check whether the chart is consistent. I
found this interesting comparison for a 200lb person*:
"Jogging at 5mph for 30 min: 370 cal."
"Walking a 15min/mi for 30 min: 200 cal."
Using P = F.v, we get (assuming no stupid mistakes here):
F = 148 cal/mi (jogging)
F = 100 cal/mi (walking)
We also find that the jog is 2.5 miles long, while the walk is 2
miles (4mph). That's a rather fast walk, but more importantly, would
suggest a metabolic level not that much different from the jog. This
calls into question the suggested 48% "efficiency improvement for
calorie burning" (my terms) of jogging over walking. I believe that
the value of F here should instead be quite roughly the same,
unless...
One can further estimate that 200lb displaced over a mile is
1,056,000 ft-lbs, or 342 nutritional calories (according to one
on-line calculator), yielding a factor mu (F = mu.N) of .43 for
jogging, and .29 for walking.
Here, mu could represent a whole slew of human factors other than
friction coefficient, but other things equal the largest factor of
discrepancy would be metabolism IMO, already argued to be not enough
under the stated conditions to explain the difference. Or do I miss
something?
*the chart appears to consistently factor the weight of the person throughout