Question

A bird travels from island A to island B flying in a straight horizontal line. The distance between the two islands is 1 km. When there is no wind, the bird usually spends 2.50 kcal of energy for flapping its wings to create lift and move forward for the whole trip. Unfortunately, during the trip, a cold wind is present and induce a drag force on the bird of 35N, against the direction of motion. In addition, the temperature of the wind is 10 ̊the bird’s surface temperature is 30 ̊C. The total time taken by the bird for the whole trip in these conditions is1 hour.

a) Identify all the processes inducing energy loss for the bird, during the flight. Give the formula to calculate each of them.

b) Explain how you would calculate the total heat lost by the bird during the flight. Explain and justify each step with your own words, no calculation is required for this question.

c) Do the calculation. What result do you get?

Parameters and constants to consider: Convection coefficient of air h = 100 ?/??, emissivity of the bird ? = 0.9, surface area of the bird = 0.28?, Boltzmann constant ?= 5.6710?/???

Answer 1