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问题 选择题

如图6-1-5所示，用一个与水平面成θ角的恒力F推质量为m的木箱，木箱沿光滑水平面运动，则在作用时间t内，下列说法正确的是(　　)

图6-1-5

A．推力F的冲量是Ftcosθ

B．重力的冲量是0

C．推力F的冲量是Ft

D．木箱的动量变化是Ft

答案

答案：C

由冲量的定义可得，力F的冲量IF＝Ft，选项A错,C对.重力的冲量IG＝mgt，选项B错.由动量定理知，木箱的动量变化Δp＝Fcosθ·t＝Ftcosθ，选项D错.

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Earth Hour started in Sydney o_小题1:_ March 31, 2007. M 小题2:  than two million homes and Businesses turned off their lights for an hour. A year 1 小题3:   , in 2008, Earth Hour became the world's activity and was supported by m小题4:of people from thirty-five countries. In 2009, over two thousand cities in the world took part in it, and Earth Hour came to China.  The purpose of the activity is to save energy and improve climate. Earth Hour has b_小题5:___ some new changes  to our lives.

We may have different ways to spend the hour. For e小题6:_____, we can go to school on foot or b 小题7:    bike, plant more trees, use water more than once, never l小题8:___ the lights on  when we are not at home. Try to make full use of paper by using b 小题9:  sides. Earth Hour is a call for us to work together for a bright f 小题10:  . It is also a message of hope and action.  Everyone can make a difference.  The improvement （改善）of our environment n 小题11:  everyone's efforts（努力）. Come on! J小题12:__ us in Earth Hour 2010!
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多项选择题

债务资金的主要来源是（）。

A.自有资金

B.信贷融资

C.债券融资

D.融资租赁
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