Is James Charles a boy or a girl ? I am so confused

By what factor is the heat flow increased if a window 0.550 mm on a side is inserted in the door? The glass is 0.450 cmcm, and t

Andrei [34K]

This question is incomplete, the complete question is;

A carpenter builds a solid wood door with dimensions 1.95 m × 0.99 m × 4.5 cm . Its thermal conductivity is k=0.120W/(m.K). The air films on the inner and outer surfaces of the door have the same combined thermal resistance as an additional 1.6 cm thickness of solid wood. The inside air temperature is 19.0°C , and the outside air temperature is -6.50°C .

a) What is the rate of heat flow through the door?

b) By what factor is the heat flow increased if a window 0.550 m on a side is inserted in the door? The glass is 0.450 cm , and the glass has a thermal conductivity of 0.80 W/(m.K). The air films on the two sides of the glass have a total thermal resistance that is the same as an additional 12.0 cm of glass.

Answer:

a) the rate of heat flow through the door is 97 watts

b) The factor of increased heat flow is 1.353

Explanation:

Given that;

room dimension = 1.95m × 0.99m × 4.5cm,

thermal conductivity = 0.120 w/m.k

additional thickness of solid wood Δt = 1.6 cm

a)

first we determine the effective thickness of the door;

t = 4.5cm + 1.6 cm = 61 cm ≈ 0.061 m

Now rate of heat flow is given by the relation

Q = KA( (TH -TC)/L)

= 0.12 × (1.95 m × 0.99 m) × ( (19°C - (-6.50°C)) / 0.061m)

= 0.23166 × 418.0327

= 96.8414 watts

Q = 97 watts

therefore the rate of heat flow through the door is 97 watts

b)

by intensity the glass of thickness 0.450 cm

the effective thickness is

L = 0.45cm + 12 cm = 12.45 cm = 0.1245 m

additionally area of glass A = (0.550 m)²

A = 0.3025 m²

Now

Qglass = KA ((TH-TC)/L)

= 0.80 w/m.k × 0.3025 m² × (19°C - (-6.50°C)) / 0.1245m)

= 0.242 × 204.819

Qglass = 49.57 watt

Qwood = KA ((TH-TC)/L)

area of wooden door = (1.95×0.99) - 0.3025 m² = 1.628m²

so Qwood = 0.12 × 1.628 × (19°C - (-6.50°C)) / 0.061m)

= 0.19536 × 418.0327

Qwood = 81.67 watt

Q = Qglass + Qwood

Q = 49.57 watt + 81.67 watt

Q = 131.24 watt

The factor of increased heat flow is;

f = 131.24 watt / 97 watts

f = 1.353

8 0

3 years ago

In 11.8 s, 151 bullets strike and embed themselves in a wall. The bullets strike the wall perpendicularly. Each bullet has a mas

Aneli [31]

Answer:

a. ΔP/Δt = 42.6 N

b. F = 42.6 N

c. P = 142042.4 Pa = 1.42 KPa

Explanation:

a.

First, we find the change in momentum of the bullets. For one bullet:

ΔP = m(Vf - Vi)

where,

ΔP = Change in Momentum = ?

m = mass of bullet = 5 x 10⁻³ kg

Vf = Final Speed = 1110 m/s

Vi = Initial Speed = 0 m/s (Since bullets are initially at rest)

Therefore,

ΔP = (3 x 10⁻³ kg)(1110 m/s - 0 m/s)

ΔP = 3.33 N.s

For 151 bullets:

ΔP = (151)(3.33 N.s)

ΔP = 502.83 N.s

Now, dividing this by time interval, Δt = 11.8 s

ΔP/Δt = 502.83 N.s/ 11.8 s

ΔP/Δt = 42.6 N

b.

According to Newton's Second Law, the force is equal to rate of change of linear momentum:

Average Force = F = ΔP/Δt

F = 42.6 N

c.

The pressure is given by:

Average Pressure = P = Average Force/Area

P = 42.6 N/ 3 x 10⁻⁴ m²

P = 142042.4 Pa = 1.42 KPa

4 0

3 years ago

A ski lift is used to transport people from the base of a hill to the top. If the lift leaves the

Liono4ka [1.6K]

The energy of the ski lift at the base is kinetic energy:
$K= \frac{1}{2}mv^2$
where m is the mass of the ski lift+the people carried, and $v=15.5 m/s$ is velocity at the base.
As long as the ski lift goes upward, its velocity decreases and its kinetic energy converts into potential energy. Eventually, when it reaches the top, its final velocity is v=0, so no kinetic energy is left and it has all converted into gravitational potential energy, which is
$U=mgh$
where $g=9.81 m/s^2$ and h is the height at the top of the hill.

So, since the total energy must conserve, we have
$U=K$
and so
$mgh = \frac{1}{2}mv^2$
from which we find the height:
$h= \frac{v^2}{2g}= \frac{(15.5m/s)^2}{2\cdot 9.81 m/s^2}=12 m$

8 0

3 years ago

How does the water cycle transport energy and matter

natali 33 [55]

Explanation:

Water evaporates from the surface of the earth and through the leaves of the plants and trees by absorbing the heat energy from the surrounding.

This water then converts into vapour and goes up into the atmosphere where the temperature is low in the troposphere and condenses to form the clouds. During the cloud formation the heat form the vapour is absorbed in the troposphere.

These clouds when get saturated then fall in the form of precipitation of water, snow etc. Replenishing back the water of the earth.

7 0

3 years ago

Does electrons have more mass than neutrons?

musickatia [10]

Answer:

No, neutrons have about the same mass as a proton, but both have more mass than electrons.

Hope this helps a bit,

Flips

3 0

3 years ago