阅读理解
After I visited my elder sister's house, I was reminded just how different the apartment living with a child was. She has a nice big house with a few floors, a big backyard and lots of toys. Her house is my son Tom's little piece of heaven. At her house there are little toys, big toys, a doll house, a play house and more! There are bedroom stocked with train tables, ride-on toys and big trucks.
The main difference about being an apartment mom is that you cannot become a collector of “things”. I continually get rid of anything too large. When Tom was born, we made a rule that there would never be any stuffed animals in our apartment that were larger than him at that time. We also made a rule that we would only ever have at most five stuffed “anything” at one time. So far this had worked out well for us. These rules left Tom with a few special soft creatures to play with, but that can be easily put away.
Since we want to keep the appearance of being clean city dwellers, we have limited Tom's play things to one toy basket in the main living space and one big storage bin in his bedroom. I am constantly thinking about living space when I buy anything for our little Tom. We love the storage bin in Tom's room. It is filled with fun play things. It is a place to keep his toys and everything gets pulled in and out daily. Anything that doesn't fit is often weeded out to create space.
Tom absolutely likes going to his aunt's house and pulling out every single toy available to him. Of course, Tom does not notice that when he returns home he only gets one basket of toys instead of many rooms of toys. Right now Tom lives fully in his 1,100-square-foot apartment and seems very satisfied with his basket of toys.
时刻，将一金属小球从弹簧正上方某一高度处由静止释放，小球落到弹簧上压缩弹簧到最低点，然后又被弹起离开弹簧，上升到一定高度后再下落，如此反复。通过安装在弹簧下端的压力传感器，测出这一过程弹簧弹力
随时间
变化的图像如图（乙）如示，则
