如图，轻绳OA一端系在天花板上，与竖直线夹角37°，轻绳OB水平，

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问题问答题计算题

如图，轻绳OA一端系在天花板上，与竖直线夹角37°，轻绳OB水平，一端系在墙上，O点处挂一重为40N的物体．（cos37°="0.8，"sin37°=0.6）求OA、OB的拉力各为多大？

答案

参考答案：

50N；30N

解析：

如图所示由于物体处理平衡状态则有

F_OA=F₂=

F_OB=F₁=

单项选择题

Questions 11 to 18 are based on the conversation you have just heard.

A．The government has adopted many effective ways to stop pollution.

B．The government can’t prevent pollution completely because of development.

C．There are no effective purifying devices to prevent or stop pollution.

D．The government won’t control pollution even for tile sake of people’s health.

解答题

25×2=	4×500=	490÷7=	45×2=	36-12÷6=
14×5=	78÷3=	8×9+8=	210÷3=	9×0+12=