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Ostrovityanka [42]
4 years ago
7

Homes are often insulated with fiberglass insulation in their walls and ceiling. The thermal conductivity of fiberglass is 0.040

W/(m?K).Suppose that the total surface area of the walls and roof of a windowless house is 470m2 and that the thickness of the insulation is 17cm .At what rate does heat leave the house on a day when the outside temperature is 30 ?C colder than the inside temperature?
Physics
1 answer:
Murljashka [212]4 years ago
3 0

Answer:

2.866 x 10^8 J

Explanation:

Thermal conductivity, K = 0.040 W/m^2 k

Area of the wall, A = 470 m^2

Thickness, d = 17 cm = 0.17 m

difference in temperature, ΔT = 30° C

The rate of heat flow is H.

Time, t = 1 day = 1 x 24 x 60 x 60 second = 86400 second

By use of formula of heat flow

H=\frac{K A \Delta T}{d}t

H=\frac{0.040 \times 470 \times 30}{0.17}\times 86400

H = 2.866 x 10^8 J

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A cannonball with a mass of 1.0 kilogram is fired horizontally from a 500.-kilogram cannon, initially at rest, on a horizontal,
vfiekz [6]
The impulse J is equal to the magnitude of the force applied to the cannonball times the time it is applied:
J=F \Delta t
But the impulse is also equal to the change in momentum of the cannonball:
J=\Delta p
If we put the two equations together, we find
F \Delta t= \Delta p
And since we know the magnitude of the average force and the time, we can calculate the change in momentum:
\Delta p= F \Delta t=(8.0 \cdot 10^3 N)(1.0 \cdot 10^{-1} s)=800 kg m/s
7 0
3 years ago
A bird is flying due east. Its distance from a tall building is given by x(t) = 28.0 m + (12.4 m/s)t – (0.0450 m/s3)t3. What is
Kruka [31]

Answer:

3.76 m/s

Explanation:

Instantaneous velocity: This can be defined as the velocity of an object in a non uniform motion. The S.I unit is m/s.

v' = dx(t)/dt..................... Equation 1

Where v' = instantaneous velocity, x = distance, t = time.

Given the expression,

x(t) = 28.0 m + (12.4 m/s)t - (0.0450 m/s³)t³

x(t) = 28 + 12.4t - 0.0450t³

Differentiating x(t) with respect to t.

dx(t)/dt = 12.4 - 0.135t²

dx(t)/dt = 12.4 - 0.135t²

When t = 8.00 s.

dx(t)/dt = 12.4 - 0.135(8)²

dx(t)/dt = 12.4 - 8.64

dx(t)/dt = 3.76 m/s.

Therefore,

v' = 3.76 m/s.

Hence, the instantaneous velocity = 3.76 m/s

8 0
3 years ago
A sealed container holding 0.0255 L of an ideal gas at 0.981 atm and 65 ∘ C is placed into a refrigerator and cooled to 41 ∘ C w
user100 [1]

Answer:

0.911 atm

Explanation:

In this problem, there is no change in volume of the gas, since the container is sealed.

Therefore, we can apply Gay-Lussac's law, which states that:

"For a fixed mass of an ideal gas kept at constant volume, the pressure of the gas is proportional to its absolute temperature"

Mathematically:

p\propto T

where

p is the gas pressure

T is the absolute temperature

For a gas undergoing a transformation, the law can be rewritten as:

\frac{p_1}{T_1}=\frac{p_2}{T_2}

where in this problem:

p_1=0.981 atm is the initial pressure of the gas

T_1=65^{\circ}+273=338 K is the initial absolute temperature of the gas

T_2=41^{\circ}+273=314 K is the final temperature of the gas

Solving for p2, we find the final pressure of the gas:

p_2=\frac{p_1 T_2}{T_1}=\frac{(0.981)(314)}{338}=0.911 atm

3 0
4 years ago
Explain how electric currents flow only in closed circuits​
Fed [463]

Answer:

The wires are connected to both terminals of the battery, so they form a closed loop. Most circuits have devices such as light bulbs that convert electrical energy to other forms of energy. ... When the switch is turned on, the circuit is closed and current can flow through it.

Explanation:

4 0
3 years ago
Read 2 more answers
What is the speed of the tip of the minute hand of a clock where the hand is of length 7cm?​
azamat

Explanation:

Q1) What is the speed of the tip of the minute hand of a clock where the hand is of length 7cm?

Ans1) speed, v=st=2πrT=2×227×7×10-260×60=119×10-4=1.22×10-4m/s

<h2><em><u>Hope it helps</u></em></h2>
5 0
3 years ago
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