A 10 kg migratory swan cruises at 20 m/s. A calculation that takes into ac- count the necessary forces shows that this motion requires 200 W of mechanical power. If we assume an efficiency similar to humans (say, 25%), a reasonable assumption, then the metabolic power of the swan is significantly higher than this. The swan does not stop to eat during a long day of flying; it get the energy it needs from fat stores. Assuming an efficiency similar to humans, after 12 hours of flight, a. How far has the swan traveled? b. What fraction of its body mass does it lose? Assume that I g of fat contains 37 kJ of energy.

total distance moved by the swan is

d = 864000 m

Fraction of total mass lost by it

Explanation:

As we know that swan cruises at 20 m/s speed

Part a)

Distance moved by the swan is product of speed and time

so we have

Part b)

As we know that power consumed by the swan is 200 W

so total energy consumed in 12 hours is given as

Since we know that output power is 25% of total energy used so total energy consumed is given as

now we know that 1 g of fat is lost for 37 kJ energy

so total mass lost in this

so fraction of mass lost is given as

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.