Человек, плывя, держит курс перпендикулярно к течению реки со скоростью 4,7 м/с, переплывает реку шириной 339 м. Величина скорости течения реки — 1,8 м/с. В ответе укажи перемещение плывущего человека от начала движения.

Решение: в отличие от предыдущий задачи, автомобиль движется первую половину времени с одной скоростью 40 км/ч, а вторую половину времени — со скоростью 60 км/ч. Следовательно, автомобиль проходит за равные промежутки времени разные расстояния.
S1 = v1 t
2
и
S2 = v2 t ,
2
тогда средняя скорость
V = S1 + S2 = v1t/2 + v2t/2 = v1 + v2 .
t t 2
Средняя скорость для этого случая оказалась равной среднему арифметическому значению скоростей.
Подставим значения скоростей и проведем вычисления:
V = 40 + 60 = 50 км/ч.
2
Средняя скорость равна 50 км/ч.

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.