题干

有一杠杆经过调节,处于水平平衡状态,所使用的钩码重均为0.5N.如图所示,在A点悬挂两个钩码,要使杠杆水平平衡,需在B点悬挂____个钩码.取走悬挂在B点的钩码,改用弹簧测力计在C点竖直向上拉,使杠杆水平平衡,测力计的拉力为____ N;如改变弹簧测力计拉力的方向,使之斜向左上方,杠杆仍然水平平衡,则测力计的读数将____(选填“变大”、“变小”或“不变”).

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3,0.75,变大

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    The science fiction type of entertainment is considered by mot to be fathered by Jules Verne (A Journey to the Center of the Earth and Twenty Thousand Leagues Under the Sea) and H. G. Wells (The Time Machine and The War of the Worlds). Sei-Fi, as it is commonly shortened, is a fictional story in which science and technology have a significant influence on the characters and plot. Many such works are guesswork about what the future holds and how scientific findings and technological advances will shape humankind.

    Writing in the late 1800s, Jules Verne was remarkably successful in his 10 guesses about future technologies of air conditioning, automobiles, the Internet, television, and underwater, air, and space travel. Unbelievably, of all places from which to choose, Jules Verne guessed Tampa, Florida, USA as the launching site of the first project to the Moon, which was only 200 kilometers away from the actual 1969 location at Cape Canaveral, Florida.

    One of the best-known science fiction books is Nineteen Eighty-Four by George Orwell. Published in 1949, it was not meant as a prediction, but as a warning: Orwell was describing what he saw as the outcome of the ideas, trends, and emerging technologies of his time. Many invented terms from this novel have become common in everyday use, such as “big brother” and “doublethink”. Even the author's name has been made into an adjective—Orwellian—and has become a warning descriptor for situations where privacy is lost and the individual has no power and is completely controlled by the government. Nineteen Eighty-Four was translated into sixty-five languages within five years of its publication, setting a record that still stands.

    What helps bring science fiction into being is usually a new discovery or innovation. The author creates an analysis of the potential influence and consequences and then wraps it in a pleasant story. For example, the beginning of space exploration was followed a few years later by the Star Trek television program and movie series. The science fiction author's self-determined role is search the world of future possibilities upon the road which we are traveling.

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