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Genrish500 [490]
3 years ago
5

The temperature inside a Carnot refrigerator placed in a kitchen at 22 degree Celcius is 2 degree Celcius. The heat extracted fr

om the refrigerator is 89 MJ/h. What power is needed to operate this refrigerator?
Physics
1 answer:
Elanso [62]3 years ago
4 0

Answer: 1.79 kW

Explanation:

Given

The temperature of the refrigerator is T_L=2^{\circ}C\approx 275\ K

The temperature of the kitchen is T_H=22^{\circ}C

COP of the refrigerator is

COP=\dfrac{T_L}{T_H-T_L}=\dfrac{\text{Desired effect}}{\text{Power}}\\\\\Rightarrow COP=\dfrac{275}{22-2}=\dfrac{89}{P}\\\\\Rightarrow P=\dfrac{20}{275}\times 89=6.47\ MJ/h\ \text{or}\ 1.79\ kW

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Two loudspeakers, 4.5 m apart and facing each other, play identical sounds of the same frequency. You stand halfway between them
irga5000 [103]

Answer:

A) Frequency of Sound B = 242.85 Hz

B) Frequency at maximum sound intensity = 485.71 Hz

Explanation:

From intensity and path difference equations of sound waves;

the path difference for maximum intensity is x = nλ

Now, for minimum intensity, the path difference(x) is given as;

x = (2n - 1)(λ/2)

Since he has moved 0.35m,the total Path difference = (0.35) + (0.35) = 0.7 m

As n = 1,

0.7 = =(2(1) - 1)(λ/2)

So, (λ/2) = 0.7

And thus λ = 0.7 x 2 = 1.4m

From wavelength equation, we know that; λ = v/f and f = v/λ

Where v is velocity of sound

Thus ; frequency(min) = 340/1.4= 242.85 Hz

B) Now for max the path difference;

From earlier said, x = nλ

So at n=1 and λ = 0.7

x = 1 x 0.7 = 0.7

So following same equation for frequency, fmax = 340/0.7 = 485.71 Hz

3 0
3 years ago
A ball is kicked at 30.0 m/s at an angle of 20.0°. Beneath the tilted columns calculate the vertical and horizontal components.
RSB [31]

The velocities at time <em>t</em> are

• Horizontal:

<em>v</em> = (30.0 m/s) cos(20.0º)

• Vertical:

<em>v</em> = (30.0 m/s) sin(20.0º) - <em>g</em> <em>t</em>

(where <em>g</em> = 9.80 m/s² is the magnitude of the acceleration due to gravity)

If you only want the <u>initial</u> velocities, they are

• Horizontal:

<em>v</em> = (30.0 m/s) cos(20.0º) ≈ 28.2 m/s

• Vertical:

<em>v</em> = (30.0 m/s) sin(20.0º) ≈ 10.3 m/s

(just set <em>t</em> = 0)

As far as starting equations go, you can derive everything from the definition for average acceleration:

<em>a</em> = ∆<em>v</em> / ∆<em>t</em> = (final <em>v</em> - initial <em>v</em>) / <em>t</em>

→   <em>v</em> = <em>u</em> + <em>a</em> <em>t</em>

(here, <em>u</em> stands in for "initial <em>v</em>" and <em>v</em> is simply velocity at time <em>t</em> )

There is no acceleration in the horizontal direction, while the ball is essentially in free-fall in the vertical direction.

6 0
3 years ago
The combustion of 1.631 g of sucrose, C12H22O11(s) , in a bomb calorimeter with a heat capacity of 5.30 kJ/°C results in an incr
VLD [36.1K]

Answer:

= - 26.31 kJ

Explanation:

we know that number of moles is calculated as

Moles of C_{12}H_{22}O_{11} = \frac{mass}{molecular\ weight}

               = \frac{(1.631 g)}{(342.29 g/mol)}

                      = 0.00476 mol

Heat absorbed by calorimeter = heat\ capacity \times temperature\ rise

= 5.30 kJ/°C x (27.75 - 22.68)°C

= 26.87 kJ

Enthalpy of combustion

\Delta Hc = \frac{- 26.87}{0.00486}

= - 55290.12 kJ/mol

Negative sign shows that the heat is released

The balanced reaction

C_{12}H_{22} O_{11}(s) + 12 O_2(g) = 12 CO_2(g) + 11 H_2O(l)

ΔHc = ΔU + Δng (RT)

-55290.12 = ΔU + (12 - 12) *(RT)

\Delta U = - 55290.12 kJ/mol \times 0.00476 mol

= - 26.31 kJ

3 0
3 years ago
A hummingbird 3.4m above the ground flies 1.2 m along a straight line path. Upon spotting a flower below, the hummingbird drops
Anit [1.1K]

A = horizontal displacement of the humming bird = 1.2 m

B = vertical displacement of the humming bird = 1.4 m

C = net displacement of the humming bird from initial to final position = ?

In the triangle drawn , Using Pythagorean theorem

C = √(A² + B²)

inserting the values

C = √(1.2² + 1.4²)

C = √(1.44 + 1.96)

C = √(3.4)

C = 1.4 m

Hence the net displacement of hummingbird comes out to be 1.4 m

4 0
3 years ago
Read 2 more answers
Calculate the heat energy released when 17.7 g of liquid mercury at 25.00 °c is converted to solid mercury at its melting point.
maria [59]

Answer;

Q = 359.2-J  

Explanation;

Given that;

Constants for mercury at 1 atm  

Heat capacity of Hg(l) is 28.0 J/(mol*K)  

melting point is 234.32 K  

Enthalpy of fusion is 2.29 kJ/mol

17.7-g Hg / 200.6g/mol = 0.0882 mol Hg;

°C + 273 = 298 K;

2.29-kJ/mol = 2290-J/mol  

Q = (m x ΔT x Cp) + (m x Hf)  

Q = 0.0882-mol x (298 - 234.32) x 28.0-J/mol*K) + (0.0882-mol x 2290-J/mol)  

Q = 157.26-J + 201.978-J  

Q = 359.2-J  

Q=359-J (3 sig fig allowed due to 17.7-g given in problem)

8 0
3 years ago
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