Throw your hands in the air and scream!

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If you like roller coasters, strap in and stay tuned. We’re going to take a ride today on Engineering Works.

Some people are roller coaster people. They really like riding roller coasters: taller, steeper, faster. The more they scream, the better they like it.

These happy screams don’t happen by accident. Engineers design every one of them. Every time you swoop through the intricate turns, death-defying drops and loop-the-loops, you’re living the engineers’ dream. They measure success in how loud you scream.

For those of you who grew up on the thrills of Six Flags and Disney World, it’s a downer, but this is not a new idea. Space Mountain’s great-great-great grandfather appeared almost five-hundred years ago, in Russia. American scream-seekers got their first chance in 1827 in Mauch Chunk — that’s right, Mauch Chunk, Pennsylvania.

Since then, coasters have gotten faster, bigger and higher, and engineers have to pay more attention to the physics behind their designs. The faster a coaster goes, the more room the engineer needs to leave for turns. But height and speed aren’t the only factors the coaster designer has to consider. So-called “heartlineâ€? coasters are designed to put the geometric center of the ride’s tight spirals near riders’ hearts to reduce your risk of blacking out.

So the next time you’re standing in line to do the dips, drops, loops and backward 180-degree turns, thank an engineer for your thrills. We will wait for you here.

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Hands off!

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Nobody talks about it, but everybody knows what that is. We’re going to bring you to the edge of your seat today on Engineering Works.

It’s something everybody grows up with. Your mother probably told you several thousand times — wash your hands after you flush the toilet.

Now, let’s find out how some clever engineering makes it so you don’t have to remember to flush in public restrooms.

It’s all about light. A special kind of light, known as infrared in this case. You can’t see infrared light. Its frequency and wavelength, two things physicists use to describe light, are outside the range of light our eyes can see.

Using infrared light, engineers have developed valves that flush by remote control. That means you don’t have to touch that germ-covered handle that your mother warned you about.

This remote-controlled flush valve looks like a little black box with a tiny window in the front. Inside are two important devices. An emitter, and a receiver. The emitter shines out a constant beam of infrared light. When you get in the way of that beam, part of it is reflected back and the receiver sees it. If the receiver sees that reflected light for more than a few seconds, an integrated circuit tells the flush valve to get ready to go.

Then, when the receiver stops seeing the reflected light, it trips a switch and the toilet flushes. The system saves water and promotes good sanitation.

So, the next time you’re in a public restroom and the toilet flushes by itself, you know why. But don’t forget to wash your hands.

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