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Hey it's me Destin, welcome back to Smarter Every Day.
So today we're in the rocket van and I've got two little science helpers here right?
Kids: Yes, right.
Are you wearing your seatbelts?
OK we're gonna do something pretty interesting. Check this out.
I've got a pendulum suspended from the top of our family van
and we're just gonna drive forward, we're gonna accelerate,
so if we're going that way, which direction do you think this pendulum should go? What do you think?
3.. 2.. 1.. Go.
Kids: Yes.
Which way is it going?
Kids: My way.
That's right. It's because I'm accelerating right?
Does that make sense to you guys?
Yes sir.
OK very good, I was hoping it would make sense.
So we're gonna change it up just a little bit.
OK so now what I'm gonna do is I'm gonna replace this pendulum with a balloon.
We should see the same thing right? Let me cut this off.
So what we're gonna do is we're gonna accelerate that way
so we have the mass of the balloon and the acceleration that should net in a force and will have to react with this string right?
You guys ready?
Yes sir.
3.. 2.. 1.. Go.
Wait a second. What just happened?
What happens when I stop?
The balloon goes backwards when I stop.
What's happening?
3.. 2.. 1..Go.
There it is. It's coming right at me.
Why's it doing that?
Do you wanna know?
Alright, I brought something to show you.
You remember I told you I was gonna bring this jar earlier? Remember that?
So it's like this. Imagine this entire van is just like this jar,
and all the air inside this van is just like the water in the jar. Does that make sense?
So let's imagine that the balloon is this bubble on top,
because the helium in the balloon is lighter than air right?
So that causes it to do what?
Kids: Go up.
Go up, that's right.
So if I've got this air that's just like it, what happens if I move the jar that way?
All that water sloshes to the back.
And when that water sloshes back this way, which direction does the bubble go?
You see that? So the air bubble moves in the direction of acceleration,
does that make sense?
I know you're five but I think you can get this.
OK so I've got my seatbelt on. If I drive forward real fast right now which direction is the balloon gonna go?
Why will it go forward?
Because all the air's sloshing back.
That's right! Very good! Watch this.
Look at that. You see that?
So you know what that means don't you?
That means you have more air to breathe than daddy does when I'm going fast.
Did you realise that?
Kids: Nooo!
Yeah that means when I go fast, that means more air sloshes back there to you and you have more oxygen to breathe.
Doesn't it feel good back there?
OK so now we have the plumb bob right next to the balloon, so if I go forward they should spread apart right?
Let's check it out.
Is it working?
Kids: Yeah.
So what I want to do is I want to tell everybody on Smarter Every Day that if they go download
a free audio book that it'll help Smarter Every Day by sponsoring us.
Audible will, if they go to audible.com/smarter.
And so they get a free audio book, but I'm gonna do it in a funny way.
Now lean in towards me and look straight at the camera.
I know you don't know what I'm gonna do but don't laugh
because I want people to realize that they can send you to school if they get a audio book.
Does that make sense?
So whatever happens don't laugh. OK?
Look straight at the camera. Ready?
You don't know what I'm doing, do you?
OK you ready?
(High pitched helium voice) Thank you for supporting Smarter Every Day and if you would please download an audio book at audible.com/smarter.
Did you know daddy could talk like this?
You didn't know that happened, did you?
So if you go get a free audio book it'll support Smarter Every Day and it'll help me send these kids to school.
Does that sound like a good idea?
You should never do that, by the way. That's only for adults.
How'd you do that?
It's magical. Anyway I'm Destin, you're getting Smarter Every Day.
Please subscribe to Smarter Every Day and support our sponsor audible,
I'll leave a link somewhere and you can check it out.
Thanks, bye.
How'd you change your voice?
OK now we have the sunroof, the side window and the back open.
I'm gonna go forward, where do you think it's gonna go?
Daughter: Forward.
Son: Backwards.
3.. 2.. 1..
Dad: So this is air, not helium?
Yes sir.
OK I think it's gonna act like the pendulum.
Dad: 3.. 2.. 1.. Go.
(laughs) Backwards.
Oh it does. We're gonna use that one.


物理教學 慣性定理 (A Baffling Balloon Behavior - Smarter Every Day 113)

48993 分類 收藏
黃翊丞 發佈於 2014 年 5 月 11 日
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