题目

有一质量m＝2kg的物体在水平面上沿直线运动，0时刻起受到与运动方向在一条直线上的力F作用，其F﹣t图象如图（a）所示，物体在第2s末至第4s末的速度﹣时间关系图象v﹣t图如图（b）所示． （1） 根据图象计算第2s末到第4s末物体运动过程中的加速度大小； （2） 计算第2s末到第4s末的时间内物体克服摩擦力所做的功； （3） 已知两图象所取正方向一致，通过定量计算在图（b）中完成0～6s内的全部v﹣t图．30、Why do dogs chase（追赶） cats?-- Here is a story about this. One day Cat and Dog get married. They are very happy together, but every night when Dog comes home from work, Cat says she is too sick to make dinner for him. Dog is patient（有耐心的） with her at first, but soon gets tired of making dinner after a day’s hard work. After all, Cat just stays at home all day long. One day, Dog tells Cat he is going to work, but he hides in a box and wants to find if she is really sick. Cat thinks dog leaves, so she starts playing outside with other cats. They laugh and run about. Dog knows Cat isn’t sick at all. He jumps out of the box.. Dog is so angry that he starts chasing her all over the house. And dogs still like chasing cats today. 根据短文内容，选择正确答案。 1.        go（es） to work every day? A．Cat                     B．Dog           C．Cat and dog         D．neither of them 2. Cat doesn’t want to make dinner for Dog because_________? A．she’s sick            B．she’s busy     C．she’s lazy            D．she’s old 3. Dog hides in the box in order to find out _______. A．if Cat is really sick                      B．if Cat stays at home C．if Cat cooks dinner for him               D．if someone cones to his house 4. After Dog’s leaving, Cat ___________. A．stays at home all day long              B．goes outside and play C．cooks dinner at once                  D．goes to the hospital 5. When Dog finds that Cat lies to him, he is very____. A．happy                B．tired           C．relaxed                      D．angry 评卷人 得分 六、阅读填空 （每空？ 分，共？ 分）