问题
不定项选择
如图所示，是一种测定风力的仪器的原理图，质量为m的金属球，固定在一细长的轻金属丝下端，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的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=
答案
答案：B
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如图所示，是一种测定风力的仪器的原理图，质量为m的金属球，固定在一细长的轻金属丝下端，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的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=
答案：B
I’m taking my family to Europe to have a trip. My wife (妻子) and our two children are 1 going along. My brother is 2 to go with us for vacation. Because he 3 went to other countries, he is even more 4 than the children. He can’t wait to go. My father would like to stay at home, but we’ll send him postcards 5 Europe. We’re 6 next Friday. We’re going to New York by train, 7 taking a ship to Europe. When we 8 in Europe, we are going to 9 countries for sightseeing. We’re going to those places by train or by bus and we’re 10 a week there. Then we are flying home.
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