题目

---Everyone should start to act to go green. Then which of the following actions is not part of green life? ---You’re right. We should not ___________. A. do more exercise and watch less TVB. drive to work or school as much as possible C. reusing water if possibleD. take shorter showers 答案：B质量为2kg的物体静止在足够大的水平地面上，物体与地面间的动摩擦因数为0.2，最大静摩擦力与滑动摩擦力大小视为相等。从t=0时刻开始，物体受到方向不变、大小呈周期性变化的水平拉力F的作用，F随时间t的变化规律如图所示。重力加速度g取10m/,则物体在t=0到t=12s这段时间的位移大小为 A.18m              B.54m              C.72m                 D.198m