A 68 kg cyclist is pedaling down the road at 15 km/h, using a total metabolic power of 480 W. A certain fraction of this energy is used to move the bicycle forward, but the balance ends up as thermal energy in his body, which he must get rid of to keep cool. On a very warm day, conduction, convection, and radiation transfer little energy, and so he does this by perspiring, with the evaporation of water taking away the excess thermal energy. To keep from overheating, the cyclist must get rid of the excess thermal energy generated in his body. If he cycles at this rate for 2 hours, how many liters of water must he perspire, to the nearest 0.1 liter?A. 0.4 L                   B. 0.9 L                 C. 1.1 L            D. 1.4 L

A 68 kg cyclist is pedaling down the road at 15 km/h, using a total metabolic power of 480 W. A certain fraction of this energy is used to move the bicycle forward, but the balance ends up as thermal energy in his body, which he must get rid of to keep cool. On a very warm day, conduction, convection, and radiation transfer little energy, and so he does this by perspiring, with the evaporation of water taking away the excess thermal energy. If the cyclist reaches his 15 km/h cruising speed by rolling down a hill, what is the approximate height of the hill?A. 22 m                  B. 11 m              C. 2 m               D. 1 m

A 68 kg cyclist is pedaling down the road at 15 km/h, using a total metabolic power of 480 W. A certain fraction of this energy is used to move the bicycle forward, but the balance ends up as thermal energy in his body, which he must get rid of to keep cool. On a very warm day, conduction, convection, and radiation transfer little energy, and so he does this by perspiring, with the evaporation of water taking away the excess thermal energy. As he cycles at a constant speed on level ground, at what rate is chemical energy being converted to thermal energy in his body, assuming a typical efficiency of 25% for the conversion of chemical energy to the mechanical energy of motion?A. 480 W             B. 360 W             C. 240 W            D. 120 W

A pronghorn antelope can run at a remarkable 18 m/sm/s for up to 10 minutes, almost triple the speed that an elite human runner can maintain. For a 32 kgkg pronghorn, this requires an astonishing 3.4 kWkW of metabolic power, which leads to a significant increase in body temperature. If the pronghorn had no way to exhaust heat to the environment, by how much would its body temperature increase during this run? (In fact, it will lose some heat, so the rise won't be this dramatic, but it will be quite noticeable, requiring adaptations that keep the pronghorn's brain cooler than its body in such circumstances.) Assume the efficiency of the pronghorn to be equal to that of human.

When air is inhaled, it quickly becomes saturated with water vapor as it passes through the moist upper airways. When a person breathes dry air, about 25 mg of water are exhaled with each breath. At 12 breaths/min, what is the rate of energy loss due to evaporation? Express your answer in both watts and Calories per day. At body temperature, the heat of vaporization ofwater is Lv = 24 × 105 J/kg.

Overall, 80% of the energy used by the body must be eliminated as excess thermal energy and needs to be dissipated. The mechanisms of elimination are radiation, evaporation of sweat (2,430 kJ/kg), evaporation from the lungs (38 kJ/h), conduction, and convection. A person working out in a gym has a metabolic rate of 2,500 kJ/h. His body temperature is 37°C, and the outside 5.6696 x 10-8 W/m2 · K4) temperature 22°C. Assume the skin has an area of 2.0 m2 and emissivity of 0.97. (o %D (a) At what rate is his excess thermal energy dissipated by radiation? (Enter your answer to at least one decimal place.) 136.7 Your response differs from the correct answer by more than 10%. Double check your calculations. W (b) If he eliminates 0.44 kg of perspiration during that hour, at what rate is thermal energy dissipated by evaporation of sweat? (Enter your answer to at least one decimal place.) W (c) At what rate is energy eliminated by evaporation from the lungs? (Enter your answer to at least one…

Sweating is one of the main mechanisms with which the body dissipates heat. Sweat evaporates with a latent heat of 2 430 kJ/kg at body temperature, and the body can produce as much as 1.5 kg of sweat per hour. If sweating were the only heat dissipation mechanism, what would be the maximum sustainable metabolic rate, in watts, if 80% of the energy used by the body goes into waste heat?

When someone has a fever, his or her body temperature might increase by as much as 2°C. Suppose this person has a mass of 48 kg. (a) About how much energy is required to raise a person’s temperature this much? The energy required to raise the person’s temperature is ___J (b) What is this energy in food calories? (1 food calorie ≡ 1 Cal ≡ 1000 calories = 1 kcal.) The energy in food calories is ___cal

A person's basal metabolic rate (BMR) is the rate at which energy is expended while resting in a neutrally temperate environment. A typical BMR is 7.22 x 10° J/day. Convert this BMR to units of watts and kilocalories (or Calories) per hour. HINT (a) watts W (b) kilocalories per hour kcal/h (c) Suppose a 1.00 kg object's gravitation potential energy is increased at a rate equal to this typical BMR. Find the rate of change of the object's height in m/s. (The acceleration of gravity is g = 9.80 m/s2.) m/s