Ask question

Ask question

All categories

3 years ago

9

Calculate the rate of heat conduction through a layer of still air that is 1 mm thick, with an area of 1 m, for a temperature of

20C

2 answers:

max2010maxim [7]3 years ago

6 0

Answer:

The rate of heat conduction through the layer of still air is 517.4 W

Explanation:

Given:

Thickness of the still air layer (L) = 1 mm

Area of the still air = 1 m

Temperature of the still air ( T) = 20°C

Thermal conductivity of still air (K) at 20°C = 25.87mW/mK

Rate of heat conduction (Q) = ?

To determine the rate of heat conduction through the still air, we apply the formula below.

$Q =\frac{KA(\delta T)}{L}$

$Q =\frac{25.87*1*20}{1}$

Q = 517.4 W

Therefore, the rate of heat conduction through the layer of still air is 517.4 W

Goryan [66]3 years ago

3 0

Answer: Rate of heat transfer q = 517.4W

Explanation:

Thermal conductivity is a material property that describes its ability to conduct heat. Thermal conductivity is the quantity of heat transmitted through a unit thickness of a material, in a direction normal to a surface of unit area,due to a unit temperature gradient under steady state conditions. It can be shown mathematically using the equation below;

Q/t = kA(∆T)/d

q = kA(∆T)/d

q = Q/t = rate of heat transfer

Q = total amount of heat transfer

t = time

k = thermal conductivity of material

A = Area

d= distance

For the case above, the material used is still air.

k for still air at 20°C and 1bara = 0.02587W/mK

A = 1m^2

d = 1mm = 0.001m

∆T = 20°C = 20K

q = 0.02587×1×20/0.001

q = 517.4W

Therefore, the rate of heat conduction through the still air is 517.4W

You might be interested in

True/false: you should begin viewing a specimen with the 10x objective lens.

Nezavi [6.7K]

You should begin viewing a specimen with the 10X objective lens that is false.

<h3>What is a lens?</h3>

An optical device known as a lens uses refraction to focus or disperse a light beam. A compound lens is made up of multiple simple lenses (elements), typically aligned along a common axis, as opposed to a simple lens, which is one solid piece of transparent material. Glass or plastic are used to make lenses, which are then polished or molded into the required shape. In contrast to a prism, which just refracts light without focusing it, a lens can focus light to create an image. In addition to focusing visible light, lenses can also be used to disperse various types of waves and radiation, such as explosive, microwave, electron, and acoustic waves.

To know more about the lens, visit:

brainly.com/question/3558537

#SPJ4

8 0

2 years ago

the 200 g baseball has a horizontal velocity of 30 m/s when it is struck by the bat, B, weighing 900 g, moving at 47 m/s. during

Ivanshal [37]

Solution :

Given :

Mass of the baseball, m = 200 g

Velocity of the baseball, u = -30 m/s

Mass of the baseball after struck by the bat, M = 900 g

Velocity of the baseball after struck by the bat, v = 47 m/s

According to the conservation of momentum,

$Mv+mu=Mv_1+mv_2$

(900 x 47) + (200 x -30) = (900 x $v_1$ ) + (200 x $v_2$ )

36300 = (900 x $v_1$ ) + (200 x $v_2$ )

$9v_1 + 2v_2 = 363$ ..............(i)

$9v_1 = 363 - 2v_2$

$v_1=\frac{363 - 2v_2}{9}$

The mathematical expression for the conservation of kinetic energy is

$\frac{1}{2}Mv^2+\frac{1}{2}mu^2 = \frac{1}{2}Mv_1^2+\frac{1}{2}mv_2^2$

$\frac{1}{2}(900)(47)^2+\frac{1}{2}(200)(-30)^2 = \frac{1}{2}(900)v_1^2+\frac{1}{2}(200)v_2^2$ ................(ii)

$(9)(14)^2+(2)(-30)^2 = (9)v_1^2+2v_2^2$

$21681 = 9v_1^2+2v_2^2$

Substituting (i) in (ii)

$21681= 9\left( \frac{363-2v_2}{9}\right)^2+2v_2^2$

$(363-2v_2)^2+18v_2^2=195129$

$(363)^2+18v_2^2-2(363)(2v_2)+(363)^2-195129=0$

$22v_2^2-145v_2-63360=0$

Solving the equation, we get

$v_2=96 \ m/s, -30 \ m/s$

The negative velocity is neglected.

Therefore, substituting 96 m/s for $v_2$ in (i), we get

$v_1=\frac{363-(2 \times 96)}{9}$

= 19

Thus, only impulse of importance is used to find final velocity.

8 0

3 years ago

PLEASE HELP ASAP!!! CORRECT ANSWER ONLY PLEASE!!!

Marat540 [252]

The last on on the image :-)

8 0

3 years ago

A copper cylinder has a mass of 76.8 g and a specific heat of 0.092 cal/g.C. It is heated to 86.5 degrees C from 19.5 degrees C.

Sladkaya [172]

Given:

The mass of the copper cylinder is: m = 76.8 g = 0.0768 kg

The change in the temperature is: T = 86.5 deg C - 19.5 deg C = 67 deg C

The specific heat is: c = 0.092 cal/g.C

To find:

Heat energy needed to heat the copper cylinder.

Explanation:

The specific heat is defined as the amount of heat energy needed to raise the temperature of a substance by one degree celcius.

The expression relating heat Q, mass m, specific heat c and temperature difference T is:

$Q=mcT$

Substitute the values in the above equation, we get:

$\begin{gathered} Q=76.8\text{ g}\times0.092\text{ Cal/g.C}\times67\text{ deg C} \\ \\ Q=473.40\text{ Cal} \end{gathered}$

Final answer:

473.40 calories of heat is required to heat the copper cylinder.

6 0

1 year ago

Which of the following must be true about an object for it to be in uniform circular motion? A.It must have zero centripetal acc

Grace [21]

In the previous section, we defined circular motion. The simplest case of circular motion is uniform circular motion, where an object travels a circular path at a constant speed. Note that, unlike speed, the linear velocity of an object in circular motion is constantly changing because it is always changing direction. We know from kinematics that acceleration is a change in velocity, either in magnitude or in direction or both. Therefore, an object undergoing uniform circular motion is always accelerating, even though the magnitude of its velocity is constant.

hope it helps

5 0

3 years ago

Read 2 more answers