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Tpy6a [65]
4 years ago
13

A person is standing outdoors in the shade where the temperature is 17 °C. (a) What is the radiant energy absorbed per second by

his head when it is covered with hair? The surface area of the hair (assumed to be flat) is 140 cm2 and its emissivity is 0.87. (b) What would be the radiant energy absorbed per second by the same person if he were bald and the emissivity of his head were 0.68?
Physics
1 answer:
Inessa05 [86]4 years ago
7 0

Answer:

a) 4.9W b) 3.82W

Explanation:

Stefan-Boltzmann law of radiation formulae:

Q/t (W) = sigma* e*A*T^4

Sigma = 5.67*10^-8 j/sm^2K^4 (Stefano Boltzmann constant)

e = emissivity

T = absolute temperature in kelvin and A = area in m^2

a) Q/t = 140/10000(m^2) * 0.87* 5.67* 10^-8* (290^4) = 4.9W

b) without hair the

Q/t = 140/ 10000(m^2) *0.68* 5.67* 10^-8* (290^4)

= 3.82W

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Answer:

False.

Explanation:

An aurora is a natural electric phenomenon that creates bright and colorful light displays in the sky. These dramatic and colorful lights are created when electrically charged particles from solar winds enter the Earth's atmosphere and interact with gases in the atmosphere.

4 0
3 years ago
Two identical objects in outer space have a head-on collision and stick together. If, before the collision, one had been moving
julia-pushkina [17]

Answer:

1.5 m/s

Explanation:

Momentum is conserved and conservation of momentum is

p₁ + p₂ = p'₁ + p'₂

or

m₁v₁ + m₂v₂ = m₁v'₁  + m₂v'₂

In our problem, after collision v'₁ will be equal to v'₂.

Since objects are identical m₁ = m₂

m(v₁+ v₂) = 2m x v'₁

(2m/s + 1m/s) = 2v'₁

v'₁ = v'₂ = 1.5 m/s

5 0
3 years ago
We experience fictitious forces due to: a. Rotation of a reference frame b. Inertial reference frames c. Translational motion d.
lisabon 2012 [21]

Answer:

A.

Explanation:

A fictional force (also called force of inertia, pseudo-force, or force of d'Alembert, 5), is a force that appears when describing a movement with respect to a non-inertial reference system, and that therefore it does not correspond to a genuine force in the context of the description of the movement that Newton's laws are enunciated for inertial reference systems.

The forces of inertia are, therefore, corrective terms to the real forces, which ensure that the formalism of Newton's laws can be applied unchanged to phenomena described with respect to a non-inertial reference system. The correct answer is A.

8 0
4 years ago
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Answer:

A

Explanation:

5 0
3 years ago
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The plane of a rectangular coil, 3.7 cm by 3.7 cm, is perpendicular to the direction of a uniform magnetic field B. If the coil
gizmo_the_mogwai [7]

Answer:3.77 T/s

Explanation:

Given

Area of cross-section=3.7\times 3.7 cm^2=13.69 cm^2

N=no of turns=61

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current (i)=0.04 A

emf induced=i\times R=0.04\times 8=0.32 V

emf induced e=NA\frac{\mathrm{d} B}{\mathrm{d} t}

0.32=62\times 13.69\times 10^{-4}\times \frac{\mathrm{d} B}{\mathrm{d} t}

\frac{\mathrm{d} B}{\mathrm{d} t}=\frac{0.32\times 10^4}{848.78}=3.77 T/s

8 0
4 years ago
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