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natita [175]
2 years ago
6

An electric power plant uses energy from burning coal to generate steam at 450∘C. The plant is cooled by 20∘C water from a nearb

y river. If burning coal provides 100 MJ of heat, what is the theoretical minimum amount of heat that must be transferred to the river during the conversion of heat to electric energy? A. 100 MJ. B. 90 MJ. C. 60 MJ. D. 40 MJ.
Physics
1 answer:
Goryan [66]2 years ago
6 0

Answer:

40 MJ (D)

Explanation:

Quantity of heat (Qh) = 100 MJ

temperature of steam (Th) = 450°c = 450 + 273 = 723 K

emperature of water (TI) = 20 °c = 20 + 273 = 293 k

efficiency = (Qh-Qi)/Qh = (Th-Ti)/Th

 \frac{100x10x^{6}-Qi }{100x10^{6}} = \frac{723-293}{723}

100x10^{6} - Qi= 0.5947 x 100 x 10 ^{6}

100x10^{6} - (0.5947 x 100x10^{6}) = Qi

Qi = 40.5 MJ equivalent to 40 MJ (D)

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#1

Volume of lead = 100 cm^3

density of lead = 11.34 g/cm^3

mass of the lead piece = density * volume

m = 100 * 11.34 = 1134 g

m = 1.134 kg

so its weight in air will be given as

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now the buoyant force on the lead is given by

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now as we know that

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0.11 = 1000* V * 9.8

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V = 11.22 cm^3

(ii) this volume of water will weigh same as the buoyant force so it is 0.11 N

(iii) Buoyant force = 0.11 N

(iv)since the density of lead block is more than density of water so it will sink inside the water


#2

buoyant force on the lead block is balancing the weight of it

F_B = W

\rho V g = W

13* 10^3 * V * 9.8 = 11.11

V = 87.2 cm^3

(ii) So this volume of mercury will weigh same as buoyant force and since block is floating here inside mercury so it is same as its weight =  11.11 N

(iii) Buoyant force = 11.11 N

(iv) since the density of lead is less than the density of mercury so it will float inside mercury


#3

Yes, if object density is less than the density of liquid then it will float otherwise it will sink inside the liquid

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What is the volume of an irregularly shaped object that has a mass 3.0 grams and a density of 6.0 g/mL
pogonyaev

Answer: The volume of an irregularly shaped object is 0.50 ml

Explanation:

To calculate the volume, we use the equation:

\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}

Density of object = 6.0g/ml

mass of object = 3.0 g

Volume of object = ?

Putting in the values we get:

6.0g/ml=\frac{3.0g}{\text{Volume of substance}}

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