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It is important for the body to have mechanisms to effectively cool itself; if not, moderate exercise could easily increase body temperatures to dangerous levels. Suppose a 70 kg man runs on a treadmill for 39 min , using a metabolic power of 1000 W. Assume that all of this power goes to thermal energy in the body.

If he couldn't perspire or otherwise cool his body, by how much would his body temperature rise during this exercise?

please help with this...

Respuesta :

You will need human body specific heat, Cp, to do the maths.

In Internet I found this data: Cp = 3470 j / kg * °C

Now transform the power to work, by: P = Work / time => Work = P * time

Work = 1000 W * 39 min * 60 min/ s = 2,340,000 j

We will use  T = 37 °C as the initial body temperature.

Now use Heat = m*Cp*ΔT = 70 kg * 3470 j / kg * °C * (T - 37°C) = 2,340,000 j

You can now isolate T = 2340000 / [70*3470] + 37°C = 46.6 °C




The rise in temperature of the man’s body due to the thermal energy during exercise is [tex]\boxed{9.63\:^{\circ}\text{C}}[/tex] .

Further Explanation:

Given:

The power generated in the body is [tex]1000\,{\text{W}}[/tex] .

The mass of the man is [tex]39\,{\text{kg}}[/tex] .

The time spent by the man on the treadmill is [tex]39\,\min[/tex] .

Concept:

The thermal energy gained by the person while performing exercise may lead to significant increase in the body temperature.

The energy imparted in the person’s body is given by:

[tex]Q={\text{power}}\times{\text{time}}[/tex]

Substitute the value of power and time.

[tex]\begin{aligned}Q&=1000\times\left({39\times60\,\sec}\right)\\&=2340000\,{\text{J}}\\\end{aligned}[/tex]

Now, the specific heat capacity of the human body is estimated to be [tex]3470\text{ J/kg}^{\circ}\text{C}[/tex] .

The heat absorbed by the man’s body can be expressed as:

[tex]Q=m\times C\times\Delta T[/tex]

Here, [tex]m[/tex]  is the person’s mass, [tex]C[/tex]  is the specific heat capacity of human body and [tex]\Delta T[/tex]  is the change in temperature of the body.

Substitute the values in above expression.

[tex]\begin{aligned}2340000&=70\times3470\times\Delta T\\\Delta T&=\dfrac{2340000}{70\times3470}\\&=9.63\:^{\circ}\text{C}\end{aligned}[/tex]

Thus, the rise in temperature of the man’s body due to the thermal energy during exercise is [tex]\boxed{9.63\:^{\circ}\text{C}}[/tex] .

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Answer Details:

Grade: College

Subject: Physics

Chapter: Heat and Thermodynamics

Keywords:

Moderate exercise, increase body temperatures, dangerous levels, metabolic power of 1000 W, thermal energy, couldn’t perspire, runs on a treadmill.