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  • Hey it's me, Destin. Welcome to Smarter Every Day.

  • Today we- (Jörg) Nope. [Chuckles]

  • Welcome to the Slingshot Channel. [Laughs]

  • (Destin) As you can see, today I've been taken over by Germans.

  • We're going to look at slingshots today.

  • The physics of slingshots.

  • So why do they call your channel the Slingshot Channel? I don't understand.

  • (Jörg) You know, I don't understand either.

  • You know, you would think that we'd call it the Nice Guys Channel

  • or something like that, so... No, they called it the Slingshot Channel.

  • - I think it makes sense. [Both laugh]

  • We're going to talk about the energy use in bands.

  • Do you want to say anything about it?

  • - Yes. Well, this is of course the lightest slingshot that I've ever built.

  • [Both laugh]

  • Not exactly. It's actually the most powerful one.

  • The energy of a rifle shot, and it has the momentum of a sledgehammer.

  • - Alright, so we'll do the math and see ifrg is right.

  • So let's look at the physics of slingshots.

  • Kinetic energy is 1/2 mass times velocity squared.

  • For a .22 it's about 153 joules,

  • but for a Springfield .30-06 it's 3841 joules.

  • I calculated the momentum of a sledgehammer by smashing bricks in the back yard

  • and analyzing the high-speed.

  • It worked out to about 46 newton seconds.

  • There is an angle between the band and the point of anchoring.

  • This angle... I'm not going to get my hand in there, 'cause I don't want to die.

  • But this angle... if you take the cosine of that angle,

  • that is the amount of force going into accelerating the projectile.

  • So the closer the bands, the more efficient the slingshot.

  • Is that correct, Jörg? - Yes, exactly.

  • - Yeah, this is as awesome as it looks.

  • [Click, wooden clang]

  • (Jörg) So because it's rather cold now,

  • and also we kept the bands in drawn out condition for quite a while,

  • the shot went low a little bit

  • because the rubber was a little bit tired already,

  • and in cold weather rubber doesn't work as well as in hot temperatures.

  • - Ah. Makes sense.

  • It was almost a complete momentum transfer between that ball and the wood.

  • The mass-times-velocity of the ball went all into the wood,

  • So the mass-times-velocity of the wood after the shot would be equal to the ball.

  • [Music]

  • [Man speaks German]

  • [Click, splat]

  • (Destin) Yes! [Laughs]

  • [Music]

  • So I'm Destin, and you are getting smarter every day.

  • And if you want to, go check outrg's channel - the Slingshot Channel.

  • Yeah? - Yes. Make sure.

  • So I'll put a link for you to click,

  • so go to his channel and if you like it, subscribe.

  • That's it. Bye.

  • (Jörg) This is the only slingshot that I've ever built

  • that makes grown men giggle like they're small girls.

  • [Both laugh]

  • - Okay, slingshots are all about turning potential energy into kinetic energy.

  • So the first thing we have to do, is we have to build up the potential energy,

  • sorg is doing that now...

  • with his sissy device.

  • [Destin giggles]

  • That translates, right? [Giggles]

  • (Jörg) Pretty much. And I will soon be done here, so...

  • - So I'll have to start running.

  • So this is a very, very large steel ball, clasped here between the dowels,

  • and we're going to try to destroy this pumpkin.

  • The pumpkin really has no chance.

  • It's just a question of if we can hit it.

  • Captioning in different languages welcome. Please contact Destin if you can help

Hey it's me, Destin. Welcome to Smarter Every Day.

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彈弓的物理學,與約爾格--每天更聰明 31 (The Physics of Slingshots, with Jörg - Smarter Every Day 31)

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    林宜悉 發佈於 2021 年 01 月 14 日
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