Pe2.1. a. if a breath of air, with a volume of 0.5 liter, is drawn into the lungs and comes to thermal equilibrium with the body at 37ºc while the pressure remains constant, calculate the increase in enthalpy of the air if the initial air temperature is 20ºc and the pressure is 1 atm.. (assume air, which is mainly n2 and o2, is an ideal diatomic gas with cv = 5r/2.)
b. at a breathing rate of 12 per minute, how much heat is lost in this fashion in 1 day?
c. compare your answer with a typical daily intake of 12,000 kj of food energy. what problems might you foresee in arctic climates, where the air temperature can reach –40ºc and below?
need with a, b and c

potential energy is directly proportional to height.

more height = more potential energy.

greatest increase in height = greatest increase in potential energy

where are the points with the greatest increase in height ?

has to be c-e or d-e .

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.