问题
问答题
牛顿第一定律是在实验的基础上经过推理得出的，如图所示，让同一辆小车从同一斜面的同一高度滑下，接着在材料不同的三个平面上继续运动，分别停在图中所示的位置，请回答：
（1）小车从同一斜面的同一高度滑下的必要性：______；
（2）我们从这个实验可以直接得到的结论是：______；
（3）我们从这个实验推理得出的结论是：______．
答案
（1）该实验要比较的是小车在阻力不同的路面上滑行的距离，这样就要求我们控制变量：初速度，而从同一点滑下，可以保证每次到达水平面的速度相同，
故（1）答案为：小车从斜面上滑下后具有相同的速度（意思同即可）．
（2）分析三个不同水平面上，我们就可以发现，三个小车主要不同为距离的不同，而产生这种现象的主要原因是因为所受阻力的不同，
故（2）答案为：阻力越小，小车滑行的距离越远．
（3）由三个水平面上距离的不同我们可以通过合理外推，想象到，如果物体不受阻力，小车速度将不再发生改变，
故（3）中答案为：运动的物体不受力时会保持匀速直线运动状态．
hat the refrigerator overheard our talk. The very next day it went wrong. The repairman told us we needed a new unit. Cost:$600. Not long after that, we got a refund（赔偿金）from the shop, enough to pay for a trip to Mexico. “I’ve something to tell you,” I said to my wife in a low voice. “How about the living-room?” she suggested. I remembered the color TV set was there. “No, not there. Let’s go out.” I showed her the check as we stood on the driveway. We held each other excitedly and hardly noticed the rain. My car was parked within5 meters. I didn’t think anything about it at the time. As I started for the airport the next day, the car began making strange sounds. Changing the engine cost about $ 1, 000.
s published and I am paid for, the word processor（文字信息处理机）is going to go for sure. It’ll know. 
n equipment in the writer’s home