木块A、B分别重50N和60N，它们与水平地面之间的动摩擦因数均为0.25。夹在A、B之间的轻弹簧被压缩了2cm，弹簧的劲度系数为400N/m，系统置于水平地面上静止不动。现用F＝1N的水平拉力作用在木块B上，如图所示，力F作用后
A．木块A所受摩擦力大小是12.5N
B．木块A所受摩擦力大小是11.5N
C．木块B所受摩擦力大小是9N
D．木块B所受摩擦力大小是7N
答案：C
| 书面表达。 | ||||||||||||
| 上周，你校对学生做了一项调查。下列表格是你根据自己的实际情况填写的内容。 | ||||||||||||
| ||||||||||||
| Oct. 5, 2010 Tuesday SunnyIn order to learn our attitudes towards some things, our school did a survey on us last week. The following is what I wrote in the form._________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ |
