A 68 kg cyclist is pedaling down the road at 15 km / h, using a total metabolic power of 480

step 1 Okay, we have Jonathan is riding a bicycle and encounters a hill that is 7 .3 meters high. At th

A 68 kg cyclist is pedaling down the road at 15 km / h,...

A $68 \mathrm{~kg}$ cyclist is pedaling down the road at $15 \mathrm{~km} / \mathrm{h}$, using a total metabolic power of $480 \mathrm{~W}$. 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. $480 \mathrm{~W}$ B. $360 \mathrm{~W}$ $\mathrm{C}_{4} 240 \mathrm{~W}$ D. 120 W

A $68 \mathrm{~kg}$ cyclist is pedaling down the road at $15 \mathrm{~km} / \mathrm{h}$, using a total metabolic power of $480 \mathrm{~W}$. 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. $480 \mathrm{~W}$
B. $360 \mathrm{~W}$
$\mathrm{C}_{4} 240 \mathrm{~W}$
D. 120 W

Key Concepts

Metabolic Power

Metabolic power is the rate at which chemical energy is expended by an organism to perform physical work and maintain bodily functions. It encompasses all the energy transformations occurring in the body and is a key factor in evaluating how efficiently the body converts stored chemical energy into mechanical force and heat.

Heat Dissipation Mechanisms

Heat dissipation mechanisms are the processes through which organisms release excess thermal energy to maintain a stable internal temperature. Common methods include conduction, convection, radiation, and evaporation (such as sweating in humans). In conditions where other methods are limited, evaporation becomes a critical pathway to remove the extra heat generated from inefficient energy conversion.

Energy Conversion Efficiency

This concept refers to the ratio of useful output energy to the total input energy. In many systems, including human physiology, only a portion of the chemical energy is converted into mechanical work, with the rest released as heat. An efficiency of 25% means that only a quarter of the energy is used for work while the remaining 75% is dissipated as thermal energy.

Energy Balance

Energy balance involves accounting for the input energy and its distribution among useful work, heat generation, and storage or dissipation. In physiological processes, understanding energy balance is crucial for determining how much energy is available for mechanical tasks versus how much must be managed or expelled, often in the form of thermal energy.

Transcript

Please give Ace some feedback