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777dan777 [17]
3 years ago
10

As a rough approximation, the human body may be considered to be a cylinder of length L=2.0m and circumference C=0.8m. (To simpl

ify things, ignore the circular top and bottom of the cylinder, and just consider the cylindrical sides.) If the emissivity of skin is taken to be e=0.6, and the surface temperature is taken to be T=30∘C, how much thermal power P does the human body radiate?
Physics
1 answer:
Brilliant_brown [7]3 years ago
4 0

Answer:

Thermal Power = 460W

Explanation:

From Stephan-Boltzmann Law Formula;

P = єσT⁴A

Where,

P = Radiation energy

σ = Stefan-Boltzmann Constant

T = absolute temperature in Kelvin

є = Emissivity of the material.

A=Area of the emitting body

Now, σ = 5.67 x 10^(-8)

є = 0.6

Temperature = 30°C and coverting to kelvin = 30 + 273 = 303K

Area ; since we are to consider the sides of the human body as 2m and 0.8m,thus area = 2 x 0.8 = 1.6

Thus thermal power = 0.6 x 5.67 x 10^(-8) x303⁴ x 1.6 = 458. 8W

Normally, we approximate to the nearest 10W. Thus, thermal power is approximately 460W

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1.) Law of Induction.

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An inventor develops a stationary cycling device by which an individual, while pedaling, can convert all of the energy expended
Eddi Din [679]

Answer:

Emec = 94050 [J]

Explanation:

In order to solve this problem, we must understand that all thermal energy is converted into mechanical energy.

The thermal energy can be calculated by means of the following expression.

Q=m*C_{p}*(T_{final}-T_{initial})

where:

Q = heat [J]

Cp = specific heat of water = 4186 [J/kg*°C]

m = mass = 300 [g] = 0.3 [kg]

T_final = 95 [°C]

T_initial = 20 [°C]

Now we can calculate the heat, replacing the given values:

Q=0.3*4180*(95-20)\\Q= 94050[J]

Since all this energy must come from the mechanical energy delivered by the exercise bike, and no energy is lost during the process, the mechanical energy must be equal to the thermal energy.

Q=E_{mec}\\E_{mec}=94050[J]

4 0
3 years ago
Una bola de 1 kg gira alrededor de un circulovrtical en el extremo de un cuerda. El otro extremo de la cuerda esta fijo en el ce
Vladimir79 [104]

Answer:

La diferencia entre las tensiones máxima y mínima es de 19.614 newtons.

Explanation:

Puesto que la bola gira en un círculo vertical, existe claramente una diferencia entre las tensiones debido a la influencia de la gravedad y la tensión que resulta de la aceleración centrípeta experimentada por la masa. La máxima tensión ocurre cuando la bola se encuentra en el nadir (o la sima) del trayecto circular, la cual se describe por la Segunda Ley de Newton:

T_{max} - m\cdot g = m\cdot \frac{v^{2}}{L}

En cambio, la mínima tensión aparece cuando la bola se encuentra en el cénit (o la cima) del trayecto circular, descrita por la misma ley de Newton:

T_{min} + m\cdot g = m\cdot \frac{v^{2}}{L}

Donde:

T_{min}, T_{max} - Tensiones mínima y máxima, medidas en newtons.

m - Masa de la bola, medida en kilogramos.

g - Constante gravitacional, medida en metros por segundo al cuadrado.

L - Distancia con respecto al eje de rotación, medida en metros.

v - Rapidez tangencial, medido en metros por segundo.

Se elimina la aceleración centrípeta de ambas expresiones por igualación:

T_{min} + m\cdot g = T_{max} - m\cdot g

Ahora, la diferencia entre las tensiones máxima y mínima es:

T_{max} - T_{min} = 2\cdot m \cdot g

Si m = 1\,kg y g = 9.807\,\frac{m}{s^{2}}, entonces:

T_{max} - T_{min} = 2\cdot (1\,kg)\cdot \left(9.807\,\frac{m}{s^{2}} \right)

T_{max}-T_{min} = 19.614\,N

La diferencia entre las tensiones máxima y mínima es de 19.614 newtons.

5 0
3 years ago
Each of three tuning forks, A, B, and C, has a slightly different frequency. When A and B are sounded together, they produce a b
a_sh-v [17]

Answer:

The smallest possible beat frequency when B and C are sounded together is 3 Hz

Explanation:

Given;

the beat frequency of A and B = 2 Hz

the beat frequency of A and C = 5 Hz

Beat frequency is equal to the difference in frequency of the two notes that interfere to produce the beats.

F_b_{(AB)} = 2 \ Hz\\\\F_A - F_B = 2 \ Hz -----equation(1)\\\\F_b_{(AC)} = 5 \ Hz\\\\F_A - F_C = 5 \ Hz-----equation(2)\\\\from \ equation(1), make \ F_A \ the \ subject \ of \ the \ formula\\\\F_A = 2H_z + F_B -----equation (3)\\\\Substitute \ in \ the \ value \ of \ F_A \ in \ equation(3) \ into \ equation(2)\\\\2H_z + F_B - F_C = 5H_z\\\\F_B-F_C = 5H_z - 2H_z\\\\F_B -F_C = 3Hz

Therefore, the smallest possible beat frequency when B and C are sounded together is 3 Hz

7 0
3 years ago
Reactance Frequency Dependence: Sketch a graph of the frequency dependence of a resistor, capacitor, and inductor. RLC Circuit R
jolli1 [7]

Answer:

f=\frac{1}{2\pi \sqrt{LC}}

Explanation:

We know that impedance of a RLC circuit is given by Z=R+J(X_L-X_C)

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So \omega L-\frac{1}{\omega C}=0

\omega ^2=\frac{1}{LC}

\omega =\sqrt{\frac{1}{LC}}

We know that \omega =2\pi f

So \omega =2\pi f=\frac{1}{\sqrt{LC}}

f=\frac{1}{2\pi \sqrt{LC}}

Where f is resonance frequency  

8 0
3 years ago
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