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How Does a Bike Stay Upright?

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If you give a bike a good push down a hill, it can ride off into the sunset without you. Moving bikes can stay upright even without a rider. Why is this? 

The folks at MinutePhysics take a look at the phenomenon: 

When a moving bike begins tilting to one side, it also automatically steers in that direction, bringing it back into balance. There are several reasons for this, physically speaking, all of which come together to help keep a bike upright:

Bikes have a steering axis that’s tilted slightly backward, toward the seat. The bike wheel makes contact with the ground slightly behind that axis, so when the bike turns, the upward force of the ground turns the wheel and handlebars in the same direction. 

The weight of the handlebars is positioned slightly in front of the steering axis. When the bike turns, the downward pull from the mass of the handlebars helps turn the wheel in the same direction. 

Gyroscopic precession, which governs how helicopters steer, also affects bikes. When a force is applied to a spinning wheel, the movement happens 90 degrees beyond where it was applied. So force applied pushing the bike left from the ground actually turns the middle of the wheel left.

The reason a slow-moving bike doesn’t stand up is that the wheel doesn’t have enough time to turn to keep the bike in balance. 

So, maybe don't push your bike down a big hill. 

[h/t: NPR

All images from MinutePhysics // Screenshots via YouTube

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Courtesy of CURIOUS GEORGE is a production of Imagine, WGBH, and Universal. Curious George and related characters, created by Margret and H.A. Rey, are copyrighted and trademarked by Houghton Mifflin Harcourt Publishing Company and using under license. Licensed by UNIVERSAL STUDIOS LICENSING LLC. Television series: (c) 2015 Universal Studios. All rights reserved.
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How a Makeshift Bicycle Saved Curious George From the Nazis
Courtesy of CURIOUS GEORGE is a production of Imagine, WGBH, and Universal. Curious George and related characters, created by Margret and H.A. Rey, are copyrighted and trademarked by Houghton Mifflin Harcourt Publishing Company and using under license. Licensed by UNIVERSAL STUDIOS LICENSING LLC. Television series: (c) 2015 Universal Studios. All rights reserved.
Courtesy of CURIOUS GEORGE is a production of Imagine, WGBH, and Universal. Curious George and related characters, created by Margret and H.A. Rey, are copyrighted and trademarked by Houghton Mifflin Harcourt Publishing Company and using under license. Licensed by UNIVERSAL STUDIOS LICENSING LLC. Television series: (c) 2015 Universal Studios. All rights reserved.

Curious George, the beloved star of children’s literature, might not exist if not for an empty bicycle shop and a handy artist.

As a new video from Great Big Story explains, the cartoon monkey was the brainchild of Hans and Margret Rey, a Jewish-German couple who lived in Rio de Janeiro in the 1930s. The two pet monkeys that the writer/illustrator duo kept there soon became the inspiration for a character they called Fifi: an impish, inquisitive monkey.

The Reys later moved to Paris, but when the Nazis invaded France, they were forced to flee, taking their manuscripts with them. When they tried to make their escape, though, they discovered that no more trains were leaving the city.

The desperate couple located a bicycle store, only to find no available bikes. Making do with what was available, Hans Rey used spare parts to jerry-rig two makeshift bikes to carry them—and the story of the monkey who would later become Curious George—to Lisbon, Portugal, where a ship to New York awaited them.

Hear the amazing true story of the Reys' journey (and learn how Fifi evolved into the George we know today) by watching the video below.

[h/t Great Big Story]

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The Netherlands Is Paving Its Roads With Recycled Toilet Paper
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There are plenty of bike lanes in the notoriously pro-cycling country that is the Netherlands, but only one is made of toilet paper. In the country's northwest province of Friesland, a 0.6-mile bike path connecting two towns is the first to be paved with recycled toilet paper, according to CityLab.

The TP helps maintain traction on slippery roads, as one expert told CityLab. The recycled toilet paper is used to add cellulose into open-graded asphalt friction course (OGFC), a type of water-permeable blacktop. This type of paving material is better at draining water, an especially important characteristic for surfaces in the Netherlands, where flood control is a necessary precaution. The cellulose helps stabilize the mixture that makes up the asphalt, known as OGAF. The recycling technology used to build the bike lane was developed by the Dutch consultants KNN and the wastewater tech company CirTec.

Two men stand on a paving machine in front of an asphalt bike lane.

There are plenty of materials that contain cellulose, but paving roads is a pretty good use for the one type of recycled cellulose that can’t be incorporated into a lot of other products: the kind that comes into regular contact with poop.

The recycled toilet paper in this case is collected during wastewater processing, where it’s separated out from all that excrement and then sterilized, bleached, and dried for reuse. People tend to not want to come in contact with things that have touched poop, though, so no amount of sterilization makes it OK to turn the product into recycled napkins or other paper products. But since toilet paper is typically a source of high-quality cellulose fibers (from wood chips or recycled paper), it would be a shame to waste it. Hence the pavement, which is mixed at such high temperatures that the manufacturing process would kill off any remaining pathogens that might possibly lurk within the post-treatment TP.

Friesland’s toilet paper asphalt has been around for about a year now, and according to CityLab writer Tiffany R. Jansen, it looks almost identical to the rest of the bike path. The toilet paper-laced asphalt has since been used to pave a parking lot and a dyke in the region, too.

As long as we’re wiping our butts with paper, we might as well recycle the results. Yes, toilet paper grows on trees, but that doesn’t mean we should waste it. Though the cellulose from the toilet paper only makes up about 5 percent of the pavement mixture with this technology, it’s still a good way to make a dent in city waste. Until everyone gets on the bidet train, that is.

[h/t CityLab]

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