BIO Human-Powered Flight Human-powered aircraft require a pilotto pedal, as in a

Question

BIO Human-Powered Flight Human-powered aircraft require a pilotto
pedal, as in a bicycle, and produce a sustained power output ofabout 0.30 hp. The Gossamer Albatross flew across the EnglishChannel on June 12, 1979, in 2h 49 min. (a) How much energy did thepilot expend during the flight? (b) How many Snickers candy bars(280 Cal per bar) would the pilot have to consume to be“fueled up” for the flight? [Note: The nutritionalcalorie, 1Cal, is equivalent to 1000 calories (1000 cal) as definedin physics. In addition, the conversion factor between calories andjoules is as follows:
1Cal = 1000 cal = 1 kcal = 4186 J. ]

Explanation / Answer

This problem is a matter of converting units andmultiplying out. An easy way to do it is, set up the conversions as aseries of multiplied fractions such that the units cancel. a) To find energy expended during the flight, converthours & minutes to seconds; horsepower to Joules or Watts( which are Joules / second). .   . 1horsepower = 745.7 Joules / second 0.3 *  745.7 Joules  * (2 + 49/ 60) hours * 60 minutes  * 60seconds    =   Total Energyoutput during the trip. .                sec                                                  hour             minute b) 280Cal   *   4186 Joules * Now we want to multiply on the TotalEnergy output needed for the trip, but that will      Snickers          Cal              put Joules on top and they won't cancel. So..., insteadof Energy / 1 Trip, flip it upside down and put Trip / Power and it all cancels fine.   Then at the endyou'll just have to invert the fraction again to get theanswer as   # Snickers / trip. 280Cal   *   4186 Joules *  Trip                 =           Trip    Snickers           Cal         Total Energy (in Joules)    Snickers Invert the number and you're done. Note: If you get an upside down start like this, you canerase the whole thing and start over, writing the fractions allupside down from the start, but I hate erasing, and this seemslike a good way to fix it.    Snickers           Cal         Total Energy (in Joules)    Snickers Invert the number and you're done. Note: If you get an upside down start like this, you canerase the whole thing and start over, writing the fractions allupside down from the start, but I hate erasing, and this seemslike a good way to fix it.

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