(单词翻译:单击)
Have you ever played under a parachute at school?
你曾在学校的降落伞下玩过吗？
You and your friends hold on the edge, flip it up toward the sky,
你和朋友站在它的边缘，把它抛向天空，
and then slip inside and watch it slowly float down on top of you.
然后闪到它的里面去，看它缓慢地飘落到你头顶上。
Or maybe you've seen a skydiver jump out of an airplane!
或者你看过跳伞运动员从飞机上跳下来吧！
After he jumps, he falls through the air, and then...he opens up his parachute!
他跳下来后，在空气中下降，然后打开降落伞！
The parachute slows the skydiver down,
降落伞让他减速，
so he falls gently towards the ground and can make a safe landing.
因此他缓缓地朝地面降落，安全着陆。
But have you ever thought about how parachutes work?
你想过降落伞是怎么工作的吗？
Well, in the end, parachutes work because of...air!
好吧，最终降落伞起作用是因为空气！
That's right! The stuff that's all around us!
你说得对！空气就是我们周围的东西！
You're breathing it right now!
你现在正在呼吸它！
And air, like everything else that you can feel, or that takes up space, is made of matter.
空气和你感受到的或占据空间的东西一样，都是由物质构成的。
That's what scientists call, just stuff!
这就是科学家们所说的物质！
Everything is made of matter!
一切都是由物质构成的！
The parachute, the air, the ocean, you, me, everything.
降落伞、空气、海洋、你、我，每样东西都是。
And since air is made up of matter, when you walk through the air,
因为空气是由物质构成的，当你穿行在空气中时，
you're actually pushing matter out of the way, with every move you make!
每走一步实际上都在推路上的物质。
But here's the thing...that matter is pushing back on you, too!
但问题是，物质也在反推你！
You probably don't feel it when you're just walking around.
你走路时可能感觉不到。
But when you start running, you might feel it a little bit.
但你开始跑时，你可能能感觉到一点儿。
And when you start to go even faster, like when you're speeding around on your bike.
你移动得更快，比如骑自行车到处跑时，
Whoa! That feeling is the air pushing against you!
哇！感觉就是空气在反推你！
And this force has a name: It's called drag.
这种力有个名字，叫做阻力。
Drag is the force of the air pushing back on you, or on anything when it moves.
阻力是作用到你或运动物体上的力。
And the faster something is moving, the more drag it feels.
物体移动得越快，感受到的阻力越大。
So, you don't really feel the force of the air as you walk around.
所以，你在走路时感觉不到空气的力。
But have you ever held your hand outside the window of a moving car?
但你曾把手伸到移动的车窗外吗？
That's some serious drag!
阻力很大！
You can feel the air pushing against your hand, and it can be hard to even keep it still!
你可以感觉到空气在推你的手，手很难保持静止！
But, have you noticed that it's easier to hold your hand flat, like this,
但你注意到手像这样平举
than it is to hold your hand so your thumb's pointing up, like this?
比手指这样指着上方容易吗？
Why do you think that might be?
你为什么会这么想呢？
It's because when you hold your hand straight up like this, more air is bumping into your hand.
这是因为你这样举手时，会有更多的空气碰到你的手。
That's means more drag!
这意味着阻力更多！
But when you put your hand flat, like this,
但当你把手这样平举时，
only a small part of your hand is pushing the air out of the way.
你的手只有一小部分在推空气。
There's less of your hand for the air to run up against, which means less drag,
你的手推空气的面积越少，阻力越小，
so your hand can glide through the air more smoothly.
这样，你的手在空气中滑动时就会更容易。
So, what if you're a skydiver, and you're jumping out of an airplane?
那么，假使你是一个跳伞者，从飞机上跳下来会怎么样？
How do you slow yourself down so you can land safely?
你怎样减速让自己安全着陆呢？
You'd want to do something that would make more air bump into you.
你应该想要更多的空气碰到你。
And that's how a parachute helps; it makes more space for the air to run into.
这就是降落伞的工作原理，它能腾出更多空间让空气进入。
So it creates more drag!
因此它能产生更多阻力！
There's so much drag on the parachute, so much air pushing against it,
降落伞上有太多的阻力，太多空气在用力推它，
that it slows down your fall, so you can land safely.
它减小你的降落速度，这样你就能安全着陆了。
Now, a lot of other things experience drag, too!
其他很多东西也在感受着阻力！
When a boat moves through the ocean, the water that pushes back against it is also making drag.
船在海上行驶时，水反向推它，产生阻力。
And cars and trucks experience drag when they're driving down a highway.
汽车和货车在高速路上行驶时也感受着阻力。
A little car feels less drag than a big truck,
小汽车感受到的阻力比大货车小，
because it has less space for air to push against it.
因为它留给空气推它的空间小。
So, drag is the force that you feel when you're moving through something,
所以，阻力是你穿过某物时感受到的力，
like the air, and that something pushes back.
就像空气一样，有东西在往回推你。
It may slow you down.
它可能会让你慢下来。
But it's what makes lots of things, from skydiving to playtime with parachutes possible!
但它也造就了很多东西，使得跳伞者用降落伞游戏成为可能！
Thanks for joining us on SciShow Kids!
感谢您收看本期的儿童科学秀！
Do you have a question about parachutes, force, or anything else at all?
你对降落伞、力或其他东西有什么疑问吗？
Ask a grownup for help, and leave us a comment down below,
找个大人帮忙在下方留言
or send us an email to kids@thescishow.com!
或发邮件至kids@thescishow.com！
And we'll see you next time!
我们下期见！
