Физика: решить тест по физике 8 класс

решить тест по физике 8 класс

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Ответ:

nisa89

17.09.2020 22:20

Moscow is the largest city in Russia, and its capital. The city is situated on both banks of the Moscow River and was founded more than 800 years ago. The largest most populous city of Russia — 12,108,257 people. The most populated of the cities completely in Europe, among the top ten cities in the world in terms of population. In Moscow, there are federal authorities of the Russian Federation, foreign embassies, the headquarters of most major Russian commercial organizations and associations. Moscow — a major global research center, presented research institutes working in many industries, such as nuclear energy, microelectronics, aerospace and others. In Moscow, there are 5 airports, 9 railway stations, 3 river ports. To date, Moscow is one of the most beautiful cities in the world. Particular attention is always fixed on the center of the city, since they are the most famous sights. Among them, prominent Kremlin and Red Square, the Bolshoi and Maly theaters, St. Basil’s Cathedral, Historical Museum, the Armoury and many others. The best place for lovers of art in Moscow is the State Tretyakov Gallery, which contains a large collection of Russian art. Another interesting collection of paintings and sculptures found at the Pushkin Museum of Fine Arts. In the heart of the capital, you can find the Historical Museum and the Armory. Both of these can tell us about the museum of Russian history more than any other place. One of the most famous religious sites in Moscow is the Christ the Savior Cathedral. It is located on the banks of the Moscow River and is known as the tallest Orthodox church in the world. View of the Cathedral of Christ the Savior is amazing with its grandeur and splendor. In addition, in Moscow there are a huge number of famous parks, squares, theaters, monuments, streets and concert halls.

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Ответ:

Dag18y5557hvvhi

26.08.2020 22:39

Все количество теплоты, полученное от сгорания m_c=0.3kg

спирта, пойдет на нагрев m_v=10kg

воды от температуры t_1=20^oC

до температуры t_2

.
$cm_v(t_2-t_1)=q m_c
\\\
t_2-t_1= \dfrac{q m_c}{cm_v} 
\\\
t_2=t_1+ \dfrac{q m_c}{cm_v}$
Удельная теплоемкость воды $c=4200 \frac{Dg}{kg\cdot ^oC}$
Удельная теплота сгорания спирта $q=2.7\cdot 10^7 \frac{Dg}{kg}$
$t_2=20^oC+ \dfrac{2.7\cdot 10^7 \frac{Dg}{kg}\cdot 0.3kg}{4200 \frac{Dg}{kg\cdot ^oC} \cdot 10kg} \approx 212.8 ^oC$
Получившаяся температура больше температуры кипения воды, поэтому вода (или ее часть) превратится в пар.
Оценим, хватит ли выделившегося количество теплоты для того, чтобы превратить в пар всю воду. К затратам на нагревание воды добавим затраты на парообразование:
$cm_v(t_p-t_1)+Lm=q m_c
\\\
Lm=q m_c-cm_v(t_p-t_1)
\\\
m=\dfrac{q m_c-cm_v(t_p-t_1)}{L}$
t_p

- температура кипения воды

- масса воды, которую удастся превратить в пар
$L=2.3\cdot 10^6 \frac{Dg}{kg}$ - удельная теплота парообразования воды
$m=\dfrac{2.7\cdot 10^7 \frac{Dg}{kg}\cdot 0.3kg-4200 \frac{Dg}{kg\cdot ^oC}\cdot 10kg\cdot (100^oC-20^oC)}{2.3\cdot 10^6 \frac{Dg}{kg}} \approx 2.06 kg$
Таким образом, вода нагреется до 100 градусов Цельсия (то есть на 80 градусов Цельсия) и, кроме этого, 2.06 кг превратятся в пар.
ответ: на 80 градусов Цельсия

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