The useful power output of Bryan Allen, who flew a human-powered airplane across the English Channel on June 12th, 1979, was about 350 W. The propellor of the airplane was driven by the pilot's legs, using a bicycle-tyoed mechanism. Using the efficiency for legs (20%), calculate the food energy he needed for the 2.5-hour trip.
foodenergy*.25=350*timeinseconds
so figure the time in seconds in 2.5hrs
Your answer will be in joules. To get Food calories,
foodcalories=energyinjoules/4200 joules
62.5
To calculate the food energy needed for the 2.5-hour trip, we will first determine the amount of work done by Bryan Allen based on his power output of 350 W and the duration of the flight.
Work (in joules) is calculated as the product of power (in watts) and time (in seconds):
Work = Power × Time
Since the time is given as 2.5 hours, we need to convert it to seconds:
Time = 2.5 hours × 60 minutes/hour × 60 seconds/minute
Time = 9,000 seconds
Now we can calculate the work done:
Work = 350 W × 9,000 seconds
Work = 3,150,000 joules
However, the given power output of 350 W represents the useful power output, taking into account the efficiency of the legs (20%). So, the total work done by the legs would be:
Total Work = Useful Power ÷ Efficiency
Total Work = 350 W ÷ 0.20
Total Work = 1,750 joules
Now, considering the energy efficiency of the human body, which is typically around 20% to 25%, we can find the food energy needed by the pilot. We use an efficiency of 20% in this calculation:
Food Energy = Total Work ÷ Efficiency
Food Energy = 1,750 joules ÷ 0.20
Food Energy = 8,750 joules
Therefore, the food energy Bryan Allen needed for the 2.5-hour trip was 8,750 joules.