题干

炎热的夏天,电风扇给我们带来了丝丝凉意。小科同学观察到教室里的电风扇吹出的风有时大有时小,爱动脑筋的他思考:电风扇吹出的风的强度与哪些因素有关呢?并对此提出了两

个猜想:

猜想一:电风扇吹出的风的强度与扇叶的转速有关;

猜想二:电风扇吹出的风的强度与距离电风扇的远近有关。

为验证上述猜想,小科同学设计了如图甲装置:将纸板B固定在支架上(支架未画出),硬质纸板A与轻杆固定后悬挂在纸板B上的转轴O处。纸板A和轻杆可绕转轴O来回自由摆动而不会与纸板B碰撞,且纸板A和纸板B两平面垂直。将电风扇放在纸板A左侧并正对纸板A,图中s是纸板A自然下垂时(虚线)到电风扇的水平距离;θ是电风扇吹动纸板A向右摆动稳定后轻杆与其自然下垂时(虚线)的夹角,θ越大,说明电风扇吹出风的强度越强。

上一题 下一题 0.0难度 选择题 更新时间:2019-02-04 02:09:23

答案(点此获取答案解析)

同类题5

完形填空。阅读下面短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项。

    Virak Mao moved from Cambodia six and a half years ago. He was an exciting and 1 12-year-old boy,looking forward to his new life in Canada but fearful he wouldn't make friends, 2 since he didn't speak English. What great progress he has 3 since then.

    First of all, he got over those early difficulties and 4 friends. Mao not only mastered 5 but won the Grade 9 French award. At school, he 6 to organize school events. Mao also 7 at school, such as cleaning the library and helping others . Mao had wanted to be an engineer 8 after struggling with chemistry, he discovered a new passion for 9. At his Buddhist temple, Mao is a leader and 10 those who came to Canada for the first time to work hard. He also 11 in cultural dancing with other temple members, donating any 12 they raise back to the temple to buy supplies for the poor. Since the summer of 2011, he has held a job at a clothing store to help 13 his family. In June, Mao 14 from C.W. Jefferys and is now in the business management program at Ryerson University.

    He is also the first winner of a new scholarship 15 by the Graduate Business Council with the purpose of helping a student, 16 wants to improve his community and in 17 of money. Awarded the scholarship in June, Mao spoke about the 18 of the award. “I was so excited. It was a huge relief for me,” he said, adding he would buy textbooks and school supplies with the award. “I am really 19 they raised this money to award me the scholarship. I just have no words. Anyone who works hard gets well 20.”