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IrinaK [193]
3 years ago
12

A runner has a temperature of 40°c and is giving off heat at the rate of 50cal/s (a) What is the rate of heat loss in watts? (b)

How long will it take for this person's temperature to return to 37°c if his mass is 90kg.
Physics
1 answer:
Andrew [12]3 years ago
5 0

Answer:

(a)  209 Watt

(b) 4482.8 seconds

Explanation:

(a) P = 50×4.18

Where P = rate of heat loss in watt

    P = 209 Watt

Applying,

Q = cm(t₁-t₂)................ Equation 1

Where Q = amount of heat given off, c = specific heat capacity capacity of human, m = mass of the person, t₁ and t₂ = initial and final temperature.

From the question,

Given: m = 90 kg, t₁ = 40°C, t₂ = 37°C

Constant: c = 3470 J/kg.K

Substtut these values into equation 1

Q = 90×3470(40-37)

Q = 936900 J

But,

P = Q/t.............. Equation 2

Where t = time

t = Q/P............ Equation 3

Given: P = 209 Watt, Q = 936900

Substitute into equation 3

t = 936900/209

t = 4482.8 seconds

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An object is considered to be in a condition of equilibrium when it is balanced with regard to all external forces.

Equilibrium:

An object is considered to be in equilibrium if both its angular acceleration and the acceleration of its center of mass are equal to zero. In layman's terms: The item must either be at rest or moving at a constant speed if it is not accelerating because F = ma (force = mass x acceleration). Even in motion, a body can be in equilibrium. This kind of equilibrium is referred to as a dynamic equilibrium.

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8 0
2 years ago
At a distance of 41 ft , an ionizing radiation source delivers 5.0 rem of radiation. How close could you get to the source and s
mash [69]

Answer:

at distance 18.33 ft no biological effects

Explanation:

given data

distance = 41 ft

radiation = 5 rem

to find out

how close get so no biological effects

solution

we know here that intensity of radiation R is inversely proportional to (radiation)²

so here equation will be

\frac{I1}{I2}  = (\frac{R2}{R1})^{2}   .............1

here I is intensity

so here I1 = 25

because for  0 to 25 there is  no detectable effects and for 25 to 100 it will . temporary decrease so

we take 25 because dose is less than 25 so we take that highest value

so

\frac{I1}{I2}  = (\frac{R2}{R1})^{2}

\frac{25}{5}  = (\frac{41}{R1})^{2}

R1 = 18.33 ft

so at distance 18.33 ft no biological effects

6 0
3 years ago
A sample of iron has the dimesions of 2 cm x 3cm x 2cm. If the mass of this rectangular-shaped object is 94g, what is the densit
s2008m [1.1K]
(2)(3)(2)=12⇒ D=M/V ⇒ D=94/12=7.8333(repeated) g/m³
6 0
3 years ago
4. Two people each have a mass of 55 kg. They are both in an
mestny [16]

Answer:

350 N

Explanation:

F=ma

f = force \\ m = mass \\ a = acceleration

m = 2(55kg) + 240kg \\ a = 1.0 \frac{m}{ {s}^{2} }

Force = 350 Newtons

4 0
3 years ago
Use Stefan's law to find the intensity of the cosmic background radiation emitted by the fireball of the Big Bang at a temperatu
Rus_ich [418]

Complete Question

Use Stefan's law to find the intensity of the cosmic background radiation emitted by the fireball of the Big Bang at a temperature of 2.81 K. Remember that Stefan's Law gives the Power (Watts) and Intensity is Power per unit Area (W/m2).

Answer:

The intensity is I  = 3.535 *10^{-6} \  W/m^2

Explanation:

From the question we are told that

    The temperature is  T = 2.81 \ K

Now  According to Stefan's law

        Power(P) =  \sigma  *  A  * T^4

Where  \sigma is the Stefan Boltzmann constant with value  \sigma  =  5.67*10^{-8} m^2 \cdot kg \cdot s^{-2} K^{-1}

  Now the intensity of the cosmic background radiation emitted according to the unit from the question is mathematically evaluated as

        I  =  \frac{P}{A}

=>      I  =  \frac{\sigma *  A  * T^4}{A}

=>      I  =  \sigma  *  T^4

substituting values

      I  = 5.67 *10^{-8}  *  (2.81)^4

       I  = 3.535 *10^{-6} \  W/m^2

       

4 0
3 years ago
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