My cousin Maria and I were riding our bikes. While we rode, we talked about her problem. She didn’t have a topic for her science project. We were swapping ideas when I started running out of breath. At the same time, the ride got bumpy and I slowed down. As Maria shot ahead of me, she said, “Didn’t you eat breakfast this morning, Pedro?” Maria likes to tease me.

When I stopped and got off my bike, I heard hissing. The air was leaking out of my back tire! There was a piece of broken glass stuck in it. “Now you’re the one with a problem,” Maria said. She had come back to check on me.

“Now I know why it was hard to ride. Remember what we learned in science class? When the tire rolls over the road, it causes friction. The more friction, the harder it is to push the wheel. As the air leaked out of my tire, it got flatter.”

“So when it got flatter, there was more surface and more friction,” Maria added.

We pushed our bikes to the gas station. I got out my patch kit and fixed the tire. When we got back onto our bikes, Maria said, “For my science project, I’m going to show the relationship between air pressure in a bike tire and how much of the tire touches the road.”

我和我表妹玛丽正在骑自行车。当我们正骑的时候，我们谈论她的问题。她对她的科研项目没有一个目标。当我开始出了一口气的时候，我们正在交换各自的想法。同时，自行车到了崎岖不平的地方，我慢了下来。玛丽在我的前面盯着我，她说，“你今天早上没有吃早餐吗，佩德罗？”玛丽似乎在取笑我。

当我停下来，下了自行车之后，我听到了嘶嘶声。我的自行车漏气了！有一小块碎玻璃扎进自行车里了。玛丽说，“现在你有问题了。”她不得不返回来帮我检查。

“现在我知道为什么它难骑了。还记得我们在科学课堂上学过的吗？当自行车在路面上滚动时，它会引起摩擦。摩擦力越大，越难推动轮子前进。当轮胎漏气后，轮胎就变瘪了。”

“因此，当轮胎变瘪后，会有更大的表面积进而产生更大的摩擦力。”玛丽补充说。

我把自行车推到了加油站，取出了我的修理包开始修理轮胎。当我们重新骑在自行车上的时候，玛丽说，“我的科研项目，打算解释自行车胎里的空气压力和轮胎接触多少地面之间的关系。”