1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Anna007 [38]
2 years ago
8

If you calculate the thermal power radiated by typical objects at room temperature, you will find surprisingly large values, sev

eral kilowatts typically. For example, a square box that is 1 m on each side and painted black (therefore justifying an emissivity e near unity) emits 2.5 kW at a temperature of 20∘C. In reality the net thermal power emitted by such a box must be much smaller than this, or else the box would cool off quite quickly. Which of the following alternatives seems to explain this conundrum best?A. The box is black only in the visible spectrum; in the infrared (where it radiates) it is quite shiny and radiates little power.
B. The surrounding room is near the temperature of the box and radiates about 2.5 kW of thermal energy into the box.
C. Both of the first two factors contribute significantly.
D. Neither of the first two factors is the explanation.
Physics
1 answer:
OverLord2011 [107]2 years ago
5 0

Answer:

best explanation of this is sentence B

Explanation:

The radiation emission of the bodies is given by the expression

     P = σ A e T⁴

Where P is the power emitted in watts, σ is the Stefan-Boltzmann constant, A is the surface area of ​​the body, e is the emissivity for black body e = 1 and T is the absolute body temperature in degrees Kelvin.

When the values ​​are substituted the power is quite high 2.5 KW, but the medium surrounding the box also emits radiation

   T box ≈ T room

    P box ≈ P room

As the two powers are similar and the box can absorbed, since it has the ability to emit and absorb radiation, as the medium is also close of the temperature of the box, the amount emitted is very similar to that absorbed, so the net change in energy is very small.

   In the case that the box is much hotter or colder than the surrounding medium if there is a significant net transfer.

Consequently, the best explanation of this is sentence B

You might be interested in
A car moving west slows down from a velocity of 50 m/s to 20 m/s in 15 seconds. What is its acceleration?
velikii [3]
Vf = Vo + at

Vf = 20 m/s
Vo = 50 m/s
a = ? 
t = 15

Therefore

20 = 50 + 15a

20 - 50 = 15a

-30 = 15a

a = -30 / 15

a = -2 m/s²
6 0
3 years ago
How are slow twitch fibers and fast twitch fibers different?
Vlad1618 [11]
Slow-twitch<span> muscles help enable long-endurance feats such as distance running.
</span>fast-twitch<span> muscles fatigue </span>faster<span> but are used in powerful bursts of movements like sprinting.</span>
4 0
3 years ago
f an arrow is shot upward on the moon with velocity of 35 m/s, its height (in meters) after t seconds is given by h(t)=35t−0.83t
inysia [295]

Answer:

The velocity of the arrow after 3 seconds is 30.02 m/s.

Explanation:

It is given that,

An arrow is shot upward on the moon with velocity of 35 m/s, its height after t seconds is given by the equation:

h(t)=35t-0.83t^2

We know that the rate of change of displacement is equal to the velocity of an object.

v(t)=\dfrac{dh(t)}{dt}\\\\v(t)=\dfrac{d(35t-0.83t^2)}{dt}\\\\v(t)=35-1.66t

Velocity of the arrow after 3 seconds will be :

v(t)=35-1.66t\\\\v(t)=35-1.66(3)\\\\v(t)=30.02\ m/s

So, the velocity of the arrow after 3 seconds is 30.02 m/s. Hence, this is the required solution.

7 0
3 years ago
Question 1
ella [17]
I think the answer maybe C
5 0
3 years ago
Read 2 more answers
An 8.75 kg point mass and a 14.0 kg point mass are held in place 50.0 cm apart. A particle of mass m is released from a point be
marysya [2.9K]

Answer

given,

mass of the = m₁ = 8.75 Kg

another mass of the object = m₂ = 14 Kg

distance between them = 50 cm

R₁ = 17 cm

R₂ = 50 -17 = 33 cm

a) Force applied due to the Mass 8.75  in +ve x- direction

F_1 = \dfrac{GM_1 m}{R_1^2}

F_1 = \dfrac{6.67\times 10^{-11} \times 8.75\ m}{0.17^2}

F_1 = 2.019\times 10^{8}\ m

Force applied due to mass 14 Kg in -ve x-direction

F_2 = \dfrac{GM_2 m}{R_2^2}

F_2 = \dfrac{6.67\times 10^{-11} \times 14\ m}{0.33^2}

F_2 = 0.857\times 10^{8}\ m

net force

F = F₁ + F₂

F = 2.019\times 10^{8}\ m - 0.857\times 10^{8}\ m

F = 1.162\times 10^{8}\ m

Using newton second law

a = \dfrac{F}{m}

a = \dfrac{ 1.162\times 10^{8}\ m}{m}

a =1.162\times 10^{8} \ m/s^2

b) As the acceleration of mass comes out to be  +ve hence, the direction will be toward the mass of 8.75 Kg

6 0
3 years ago
Other questions:
  • How has the use of computer and advance in technology changed healthcare industry
    13·1 answer
  • Which element is less reactive, an element who's atoms have seven valence electrons or an Element whose atoms have eight valence
    6·1 answer
  • Two boxes, P and Q, are at rest on a frictionless horizontal surface. A light, flexible cord connects them. The mass of P is gre
    6·2 answers
  • A satellite orbiting Earth at an orbital radius r has a velocity v. which represents the velocity if the satellite is moved to a
    6·1 answer
  • Saturn has a radius of about 9.0 earth radii, and a mass 95 times the Earth’s mass. Estimate the gravitational field on the surf
    5·1 answer
  • Why is it a better to wear a white shirt on a hot summer day instead of a black shirt?
    13·2 answers
  • Y’all wann trade in rob.lox I have a violet Valkyrie
    10·2 answers
  • 7. A loaded tractor-trailer with a total mass of 5000 kg traveling at hits a loading dock and comes to a stop in 0.64 s. What is
    14·1 answer
  • PHYSICS can somebody please answer this
    12·1 answer
  • Select the correct answer.
    8·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!