yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

How Does A Slinky Fall?


3m read
·Nov 10, 2024

[Applause] [Music]

Now, at some point growing up, most of us have been captivated by one of these: a slinky. But recently, I found out one of the most mesmerizing things about how it moves is something I'd never seen before: how it falls.

So what's so surprising about a falling slinky? Well, to help explain is Phys. Just Rod. The idea is that I hold the top end of the slinky like this and then let the bottom end dangle. So the slinky is dangling freely, and then I'm going to drop the slinky. But I want you to predict what's going to happen. Will the top end fall first? Will the bottom end fall first? Will both ends fall together, or will the two ends approach each other in the middle?

That is a tough question. When I let go, what does the bottom do? Shoot up! It's going to fall. It's grabbing! It's actually going to fall. The bottom goes up, the top goes down. It might come up together. You're going to see the top come down to the middle, and the bottom come up to the top to meet it and then drop. The top will accelerate faster than the bottom.

I reckon that the bottom will stay there; this will come down to there and then they go. All right, well, why don't we give it a shot here? I want you to try to watch the whole slinky as it falls to see what it's doing. Count it down! Right, three, two, one... The problem is it's a bit hard to tell with the naked eye just what's happening. No idea! I think it came up.

The bottom came up? I couldn't be sure; it's all too fast! Yeah, to really appreciate the physics involved, you need to see it in slow motion.

[Music]

Oh, oh gosh, that's great! That's weird! That's unbelievable. It does stay there; it just stays there, like in midair. It's suspended! What? Yeah, it doesn't move at all! How does that work? How does that work? How do you explain that?

Well, you've got to look at what's happening at the bottom end. Gravity is pulling the bottom end down, tension is pulling the bottom end up. The two forces are equal and opposite, so the bottom end remains at rest. Then, I let go at the top end; the tension in the spring changes, but it propagates down the spring coil by coil until it reaches the bottom end, and that takes about a quarter of a second. Then the bottom end falls.

So the tension doesn't actually change at the bottom end until the rest of the slinky has collapsed? Correct. The same principle applies to sporting equipment, like tennis rackets or golf clubs. When contact is made with a ball, a wave travels up the shaft, so the golfer's hands don't feel the hit until after the ball is already on its way to the hole.

Now, as a final extension on this experiment, we've tied a tennis ball to the base of the slinky. We're going to drop it and see what happens this time. Incredibly, the same thing happens! That's because the slinky has simply stretched further and reached a new equilibrium, where the gravitational force down equals the tension force up.

It didn't make a difference; it's the same thing! But that's what makes physics so interesting. That's why I keep doing experiments like this.

[Applause] [Music]

More Articles

View All
Giving Up On The Stock Market
What’s up, guys? It’s Graham here. So, for the past century, the stock market has been a tried and true method for building your wealth, making passive income, and growing your money to the point of never needing to work another day in your entire life e…
Have you LOST Your Self-Confidence? 6 POWERFUL TIPS | STOICISM
[Music] Believing in yourself is more than just a feeling; it’s a special skill, a deep way of thinking about life. One clear fact about learning about yourself is this: how much you achieve depends a lot on how confident you are in yourself. Not believin…
Dostoevsky - Don't Become A Slave to Pleasure
In /The Brothers Karamazov/, Dostoevsky compares two different types of people: Worldly People and Monks. Worldly People are slaves to pleasure, and because of that, they lose their freedom. Meanwhile, Monks give up the pursuit of pleasure, and because of…
Edgar: crowdfunding drive
Uh, my name is Thomas, and last year I made the film “George Ought to Help.” Right now, I’m working on a follow-up called “Edgar the Exploiter.” It will be similar to George in that it will be a gentle pro-liberty propaganda piece, because George was a s…
Warren Buffett: Why Gold is a Bad Investment
Okay, so it’s no secret that the United States, and frankly, the entire world is experiencing high levels of inflation that most countries around the world haven’t experienced in decades. You’re probably seeing this inflation, which refers to things that …
How To Get Rich In Your 20s (Realistically)
What’s up guys, it’s Graham here. So unfortunately, it’s widely believed that Millennials are the most financially screwed generation in history. After all, mortgage rates are at their most expensive level since 2001. Food prices are rising at the fastest…