How can a bicycle freewheel? A bicycle can freewheel because of a ratchet and spring-loaded catches inside the gear hub. When you cycle on a bicycle, you use the pedals to apply energy to the chain, which transfers the energy to the wheels and makes you move forwards. You want that when you are on […]
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Why do deserts have fossils? Deserts seem to have a lot more fossils because the topsoil is stripped away and because they don’t have dense vegetation. Deserts also formed in places that were good for making fossils. Many places around the world have fossils, but it seems like most of them are found in deserts.
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How did the Louisiana Purchase happen? Napoleon sold the land to the American government because he needed the money, it had lost its strategic importance, he thought Great Britain would take the land by force, and he wanted to strengthen a rival to Great Britain. In 1803, the United States bought the territory of Louisiana
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Why was the Bastille so important? The Bastille was important because it represented the absolute power and tyranny of the French monarchy. The Bastille started off life as a fortress completed in the 1380s. In the mid 14th century, the Hundred Years’ War was happening between England and France. England had invaded into France and
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Why are blue whales so big? Blue whales are so big because water can support their weight, it helps them stay warm in cold water, it helps them swim faster, they can carry more energy, and it makes feeding more efficient. Evolution tends to favor the size that gives an animal the greatest chance of
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Why do all the planets orbit in the same plane? All of the planets orbit in the same plane because they were all formed out of the same spinning cloud of gas, and because any planets that orbited at a different angle would have been less stable and could have been destroyed in collisions. The
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Why do flies seem to fly in squares in the middle of a room? This is possibly two questions. Why do flies appear to be able to make sudden right-angle turns, and why do some flies fly in a square in a room. Flies can turn so quickly because of their rapid saccadic turns. Flies
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What was the Whiskey Rebellion? It was a rebellion in the young United States over a tax on whiskey. It ended up having a big impact on the government. In 1791, the Treasury Secretary of the United States, Alexander Hamilton, managed to get his Excise Whiskey Tax passed. The United States had just won the
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When did the modern census start? The modern census developed gradually between the late 17th and mid-19th centuries. Most civilizations have had some kind of census since the beginning of civilizations. It is always important to know how many people you have in your country because then you can tax them properly and you always
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Why do mountains form in chains? Mountains form in chains because they are produced at the point where two tectonic plates meet, but there are different ways that tectonic plates can make mountains. Mountain chains are very long, often thousands of kilometers long, because the major tectonic plates are much larger than we probably imagine.
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