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Squeaks and I had an interesting adventure this morning.
今天早上，我和吱吱做了一次有趣的冒险。
Last night, it was snowing when we went to sleep,
我们昨晚睡觉时下雪了，
and when we got up today there was a bunch of snow on the ground!
今天起床后发现地上有一堆雪！
And there's this great hill in the park behind the Fort, and Squeaks wanted to go sledding.
沃斯堡后面的公园里有一座大山，吱吱想去滑雪。
So we went out there, pulled our sled up to the top of the hill, and pushed off.
所以我们去了那儿，把雪橇拉到山顶，然后推下来。
We started to move a little bit, but then, before we could get very far...we stopped!
我们开始移了一点儿，但随后没走多远就停下了！
Now, I don't know about you, but to me that seems like kind of a silly sled ride.
我不知道你怎么想，但对我来说，这似乎是一次愚蠢的滑雪。
We barely moved before we got stuck in the snow!
我们在陷入雪里之前几乎动都没动！
What do you think, Squeaks?
吱吱，你怎么看？
Yeah, it was kind of disappointing.
嗯，确实有点儿失望。
But even though our sled ride this morning didn't work so well,
即使我们早上的滑雪效果不好，
I bet we can find a way to have an awesome sled ride when we go back to the park.
但我敢打赌我们回到公园时，一定会找到方法来一次不错的滑雪之旅。
Because with science, we can figure out why we went so slow,
因为有了科学，我们才弄明白自己为什么走得这么慢，
and how to get ourselves zooming down the hill instead!
并且如何一直冲到山下！
When we're sledding, we want to move forward as fast as we can.
我们在滑雪时，想尽可能快得向前移动。
And there are a couple of easy ways to help ourselves do just that.
有几种简单的方法可以帮我们做到。
One thing we can do is push off really hard at the top of the hill to give ourselves more speed right from the start.
一种方法是在山顶努力往下推，让我们在开始时速度更大。
We can also have more weight on the sled,
我们也可以在雪橇上增加重量，
which will keep us going for longer before we stop,
让我们在停下前走得更远，
like how it's much harder to stop a heavy bowling ball that's rolling toward you than it is to stop a lighter soccer ball.
这就像拦下朝你滚来的沉重保龄球比拦下更轻的足球还难。
That's true, Squeaks!
吱吱，这是真的！
We were already doing both of those things this morning.
早上，我们把两种办法都试了。
We pushed off really hard at the top of the hill,
我和吱吱在山顶上用力地推，
and with Squeaks and I both on the sled, there was plenty of weight to keep going.
并且我们都在雪橇上，重量足以保持前进。
But that wasn't enough!
但还不够！
We still didn't move very fast, and we stopped pretty soon after we started moving.
我们仍走不远，在开始移动不久后就停下来了。
That's because there was something that was slowing us down,
这是因为有东西使我们减速，
it was pushing back on us and stopping us from moving forward.
它往回推我们，阻止我们前进。
Something that pushes or pulls is called a force,
这种推动或拉动的东西叫做力，
and the force that was stopping us from zooming down the hill is called friction.
而阻止我们冲下山的力叫做摩擦力。
Friction is what makes it hard to slide things across each other.
摩擦力使物体之间很难滑动。
There's lots of friction if those things are rough, and less if they're smooth.
如果物体粗糙，摩擦力会很大，如果物体光滑，摩擦力会小很多。
Have you ever noticed that when you're wearing socks,
你注意过你穿袜子时，
it's much harder to slide your feet across carpet than it is to slide then across a wood floor?
脚在地毯上滑动比在木地板上滑动要难得多吗？
That's because of friction.
这是因为摩擦力。
Carpet is pretty rough,
地毯很粗糙，
so there's more friction between your socks and the carpet than between your socks and the smooth wood.
所以袜子和地毯之间的摩擦比袜子和光滑木板之间的摩擦要大。
The force of friction pushes hard against your socks as you try to slide them across the carpet.
你滑过地毯时，摩擦力会用力反推袜子。
And the same thing happened with our sled, Squeaks!
吱吱，我们的雪橇发生了同样的事！
Our sled is made of wood, so it's pretty smooth.
我们的雪橇是用木头做得，相当光滑。
But the fresh snow from last night is still soft and powdery,
但昨晚的新雪仍是柔软的粉状雪，
and that was making it hard for our sled to slide across it.
使得雪橇很难划过去。
Instead, the snow kinda bunched up underneath us,
再者，在我们往下推时，雪在下面堆积起来，
and there was lots of friction slowing us down after we pushed off.
产生很多摩擦力减慢我们的速度。
That's why we didn't go very fast or far before we stopped.
这就是我们走不远或不久就停下的原因。
So, Squeaks, if we want to go really fast next time, what do you think we should do?
所以，吱吱，如果我们想下次滑得快，该怎么做呢？
That would be one way to do it!
有一种办法！
We could wait a few days until the snow on the ground is much more packed down,
我们可以等几天，等地上的雪压实了，
so it'll be hard and smooth.
这样它就会又硬又光滑了。
But we could just pack it down ourselves right now!
但我们可以现在就把它压实！
We can go back to the hill and stomp on the snow for a while,
我们可以回到山上，在雪地上踩上一段时间，
then smooth it out to make a nice track of hard, packed-down snow for our sled.
然后把它弄平，为我们的雪橇做一个坚硬、压实的雪道。
It'll be a little more work before we can start sledding, but I think it'll be worth it!
我们在滑雪前要费点儿力，但我认为值得！
How about you, Squeaks?
吱吱，你怎么想？
OK, let's do it!
好吧，我们开始做吧！
Wow, that was awesome!
哇，很好玩！
We went back to the hill with our sled and ran around on the snow for a while to pack it down into a smooth track.
我们带着雪橇回到山上，在雪里跑了一会儿，直到把它压成光滑的轨道。
Then, we went up to the top of the hill, pushed off and zoomed all the way down to the bottom!
然后我们走到山顶，把雪橇推下去，一路急冲到山下！
With the smooth, hard snow, there wasn't as much friction pushing back on the sled after we pushed off.
由于雪又滑又硬，我们在推下雪橇后没有太多的摩擦力阻止。
So we kept going faster and faster!
所以我们变得越来越快！
Yeah! Let's go do it again!
是啊！我们再来一次吧！
Thanks for joining us!
感谢您的收看！
If you want to keep learning and having fun with Squeaks and me,
如果你想继续学习，与我和吱吱共度美好时光，
hit the subscribe button, and we'll see you next time, here at the Fort!
就点击订阅键吧，我们下期见，沃斯堡等你哦！
