题干

如图所示,是一种测定风作用力的仪器的原理图,它能自动随着风的转向而转向,使风总从图示方向吹向小球P。P是质量为m的金属球,固定在一细长钢性金属丝下端,能绕悬挂点O在竖直平面内转动,无风时金属丝自然下垂,有风时金属丝将偏离竖直方向一定角度θ,角θ大小与风力大小有关,下列关于风力F与θ的关系式正确的是(     )

A:F=mgsinθ

B:F=mgtanθ

C:F=mgcosθ

D:F=mg/cosθ

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答案(点此获取答案解析)

B

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阅读下列四篇短文,从每小题后所给的A、B、C、D四个选项中,选出最佳选项,并在答题卡上将该选项涂黑。

    Elvis Presley,who was one of the most popular American singers of the twentieth century, made the Rock & Roll music popular around the world. He sold millions of records and made many successful films, and he helped change the direction of popular music in the 1960s.

Elvis Presley was born in a poor family in 1935. His parents were simple country people who often took him to church, where he learned to sing and he never forgot the kind of songs that he used to sing in church as a child.

    When he was a teenager, Elvis moved from Tupelos to Memphis in Tennessee, where he attended high school, but he was not a good student. His only real interest was singing. He began to sing in the style that is called “country and western”.

    In 1955 he recorded some songs for his mother's birthday. The people at the recording studio liked his singing and his music. There was something different about it. It was country and western music, but it also sounded a little like the music, which black people used to sing in the American South, music kn own as “blues”.

   Shortly after that, Elvis met Tom Parker, who became his manager and arranged(安排)concerts for him across the United States and new recordings as well. Soon Elvis rose to fame all over the country. Later, Elvis went to Hollywood and began to appear in films like Love Me Tender and King Creole.

    But Elvis found it hard to live with success, like many other entertainment personalities (娱乐圈内的人士). He began to take drugs and his health began to suffer. When he died at an early age of 42 in 1977, his many millions of fans were shocked. “The King Is Dead!” the newspaper said. But today his memory and his music live on and he will always be remembered as the King of Rock & Roll.