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We've been out looking for rocks to add to our rock collection!
我们一直外出寻找岩石来增加我们的岩石收藏！
And as you can see, Squeaks and I have found a ton of awesome rocks!
如你所见，我和吱吱发现了许多漂亮的石头。
We've just put them in a box and are ready to take them back to the Fort,
我们把它们放在了箱子里，准备带回沃斯堡，
so we can learn more about them.
以便更多地了解它们。
But...it looks like we might have collected a few too many!
但似乎我们收集得太多了！
This box is really heavy...too heavy to carry!
箱子太重，搬不动！
So, I wonder if we can pull the box back to the Fort.
所以，我在想我们能否把箱子拉回沃斯堡。
Squeaks, do you want to give it a try?
吱吱，你想试试吗？
Rats! Oh...sorry, Squeaks! I mean, oh man!
真烦人！哦，吱吱，对不起。我是在感叹，噢！天哪！
That was a good try, but we're going to have to think of something else.
你努力尝试了，但我们得想其他的办法。
If you've spent some time with us recently,
如果你最近和我们在一起，
you probably know that we can use simple machines to help us do work.
可能会知道我们可以利用简单的机械完成工作。
In the past we've used levers,ramps and pulleys to help us move big, heavy things.
过去我们用过杠杆、斜坡、滑轮来搬笨重的大家伙。
But neither of those are quite the right machine for this problem.
但这些机械都不适用于这个问题。
However, there's another simple machine that I think will do the trick.
但我想还有另一种简单的机械可以成功。
This simple machine is called a wheel and axle.
这个简单的机械叫做轮子和轮轴。
You already know what a wheel is!
你知道轮子是什么！
And an axle is the bar that goes into the middle of a wheel.
轮轴是插进轮子中间的棒。
In order for a wheel to work, it has to spin.
为了让轮子运转，它必须旋转。
And a wheel spins on an axle.
而轮子在轮轴上旋转。
I bet you can think of lots of things that use wheels and axles.
我猜你能想到很多利用轮子和轮轴的物品。
Like, cars and trucks, bicycles, rollerskates, rollerblades and our wagon!
比如，汽车、卡车、自行车、溜冰鞋和我们的货车！
Of course! We can put the box in our wagon and then pull it back to the Fort.
当然，我们可以把箱子放在货车上，然后拉回沃斯堡。
Great idea as usual, thanks Squeaks!
和往常一样，这是个不错的主意，吱吱，谢谢你！
Our wagon has two axles...and two wheels on each axle.
我们的货车有两个轮轴，每个轮抽上面有两个轮子。
So we'll just put the box inside the wagon.
所以我们只需把箱子放在货车里。
Okay Squeaks, pull on the handle and the box is on the move!
吱吱，拉一下把手，箱子就动了！
We solved the problem!
我们把问题解决了！
But how do the wagon's wheels and axles help us to do work?
但货车的轮子和轮轴是如何帮我们的呢？
It all comes down to how much force we need to move the box.
这要归结于我们移动箱子所需的推力大小。
We've talked about forces before: They're the pushes and pulls that things put on each other.
我们之前讨论过力：它们是事物相互影响的推力和拉力。
In this case, the force we're concerned with is the one we use to pull on the box.
在这个例子中，我们关心的是拉动箱子使用的力。
When the box was on the ground, Squeaks tried to put a big force on the box to pull it.
箱子在地面上时，吱吱试图用很大的力拉动它。
But even though he pulled really hard, he could only move it a little bit.
但即使吱吱费力拉它，也只能拉动一点点儿。
But when the box was in the wagon, Squeaks was able to pull it all by himself easily!
但箱子放到货车上时，吱吱自己就能轻易地拉动了！
So it took less force to move the box!
所以它花更少的力移动箱子！
And that's what this simple machine does.
这就是简单机械的作用。
A wheel and axle changes how much force we need to move something.
轮子和轮轴改变了我们移动物体所需的力。
Instead of a big push or pull...we can use a much smaller one.
我们只需利用较小的力即可，不用大力推拉了。
And smaller pushes and pulls mean less work for us.
而对我们来说，更小的推力和拉力意味着更少的工作。
Because it takes less force to move heavy things,
因为轮子和轮轴只需较少的力就能移动笨重的物体，
wheels and axles make it easier to move something a long way.
使得搬着东西走远道变得容易了。
That's why they're part of so many things that help us stay on the go.
这就是它们是很多助走器具零件的原因。
And that's why you'll see wheels and axles on buses, scooters, wheelchairs...and even robot rats!
也是你在巴士、滑板车、轮椅甚至机器鼠上面看到它们的原因！
But Squeaks is one robot rat that's earned a break!
但是吱吱是一只为自己赢得休息资格的机器鼠！
Hop in, Squeaks, I'll give you a ride back to the Fort!
吱吱，跳上来，我推你回沃斯堡！
Thanks for joining us!
感谢您的收看！
If you have questions about machines or forces or anything at all,
如果你对机械或力或任何东西感兴趣的话，
just grab a grown-up and let us know in the comments below.
找个大人帮忙在下方留言，让我们知道。
Or send us an email to kids@thescishow.com!
或发邮件至kids@thescishow.com！
We'll see you next time!
我们下期见！
