如图所示，夏天洒水车在向路面洒水，可以达到降温的效果，这是因为______；如果这辆洒水车工作过程中做匀速直线运动，则它的动能将不断______，牵引力做功的功率将不断______（填“增大”“减小”“不变”）
在路面上洒水是利用了蒸发吸热的道理；洒水时车的速度不变，但洒水车的质量减小，洒水车的动能减小．同时由于洒水车做匀速直线运动，所以洒水车受到的牵引力和摩擦力为平衡力，大小相等，故该过程中车的重力减小，其对路面的压力减小，在接触面粗糙程度一定时，车与地面的摩擦力减小，故此时的牵引力也减小，故据公式P=FV可知，此时牵引力做功的功率减小．
故答案为：蒸发吸热；减小；减小．
阅读下面的短文，完成下面的表格（每空词数不限）。 Ben is twelve years old. He is in Class 5, Grade 7. He likes sports. He plays sports every day. He likes playing basketball, because he thinks it is very interesting. He often plays basketball with his friends after school. He also likes helping other students. He often helps them with homework, clean the classroom and so on. We all like him very much. Linda is fourteen years old. She is in Class 4, Grade 8. She likes music. She always listen to it after school, because she thinks it is relaxing and exciting. She also joins a music club. There she can play the piano and sing.
|