Balancing on a Bicycle: The Phenomena

iStock/Izf
iStock/Izf

Reader Brian writes in to ask "Why can you stay on a bicycle when moving, but not when it's standing still?"

Think of something like a table or a couch. It has four legs that touch the floor and form a base of support (a polygon formed by an object's contact points with the ground) and as long as the table or couch's center of gravity (the mean location of the gravitational force acting on an object, or the effective point at which gravity acts) is above this base of support, it'll be statically stable, or stable when at rest.

A bicycle, on the other hand, is statically unstable because it only has two contact points with the ground (whatever portion of the front and back wheels happen to be touching the ground) and its base of support is a line segment. A good base of support needs at least three contact points with the ground, so bikes are hard to keep upright when they're still. Bikes are, however, dynamically stable, or stable when moving forward, because steering allows a rider to move the bike's points of support around under the center of gravity and keep it balanced, often with steering adjustments small enough that the rider may not even realize they're making them. It's sort of like standing on one foot. If you don't hop around a little, and you start falling sideways, you can't recover and you fall over. If you do hop, though, you can move your foot around to keep your center of gravity above it and keep your balance.

A bike has two features that help this dynamic stability immensely: its wheels. Spinning wheels have angular momentum, and when you're sitting on a bike, you and it and its wheels make up a system that obeys the principle of conservation of angular momentum. Unless torque, or twisting force, is applied from outside the system to change the wheels' angular momentum, that momentum and the direction of the momentum remain constant. In a nutshell, once the wheels line up a certain way, they want to stay lined up like that. It's easy for you to move them, but hard for an outside force to do the same, and so the bike is easy to keep balanced but doesn't topple easily. A non-moving bike has wheels that aren't spinning and zero angular momentum, which makes it very easy for external torque to change the wheels' direction, making the bike harder to balance.

Even when staying relatively motionless, though, a rider can balance a bike with some effort. By steering the front wheel to one side or the other and moving forward and backward slightly, a rider can keep the line between the bike's two contact points with the ground under the bike and rider's combined center of gravity. You can see this physics lesson in action whenever a cyclist is stopped at a red light.
(Image at left from Wikipedia user AndrewDressel.)

That was a short and sweet way to answer Brian's direct question, but there's a lot more to bicycle physics. If you're so inclined, Wikipedia's page on bicycle and motorcycle dynamics is a good starting point to learn about some of the other internal and external forces, motions and dynamics that are involved in a simple bike ride.

Looking to Downsize? You Can Buy a 5-Room DIY Cabin on Amazon for Less Than $33,000

Five rooms of one's own.
Five rooms of one's own.
Allwood/Amazon

If you’ve already mastered DIY houses for birds and dogs, maybe it’s time you built one for yourself.

As Simplemost reports, there are a number of house kits that you can order on Amazon, and the Allwood Avalon Cabin Kit is one of the quaintest—and, at $32,990, most affordable—options. The 540-square-foot structure has enough space for a kitchen, a bathroom, a bedroom, and a sitting room—and there’s an additional 218-square-foot loft with the potential to be the coziest reading nook of all time.

You can opt for three larger rooms if you're willing to skip the kitchen and bathroom.Allwood/Amazon

The construction process might not be a great idea for someone who’s never picked up a hammer, but you don’t need an architectural degree to tackle it. Step-by-step instructions and all materials are included, so it’s a little like a high-level IKEA project. According to the Amazon listing, it takes two adults about a week to complete. Since the Nordic wood walls are reinforced with steel rods, the house can withstand winds up to 120 mph, and you can pay an extra $1000 to upgrade from double-glass windows and doors to triple-glass for added fortification.

Sadly, the cool ceiling lamp is not included.Allwood/Amazon

Though everything you need for the shell of the house comes in the kit, you will need to purchase whatever goes inside it: toilet, shower, sink, stove, insulation, and all other furnishings. You can also customize the blueprint to fit your own plans for the space; maybe, for example, you’re going to use the house as a small event venue, and you’d rather have two or three large, airy rooms and no kitchen or bedroom.

Intrigued? Find out more here.

[h/t Simplemost]

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New Study Suggests That Raphael Died from Bloodletting and Pneumonia—Not Syphilis

Fever in the mornin', fever all through the night.
Fever in the mornin', fever all through the night.
Raphael, Uffizi Museum, Wikimedia Commons // Public Domain

On April 6, 1520, Italian painter Raffaello Sanzio da Urbino—better known as Raphael—died at just 37 years old from what was reported to be a fever. While the last 500 years have given rise to various theories about the details of this illness, the most popular explanation is that Raphael’s excessive philandering led to a fatal case of syphilis.

His free-loving lifestyle wasn’t exactly a secret, and painter Giorgio Vasari popularized the idea that this behavior was linked to his untimely demise in his 1550 book, The Lives of the Most Excellent Painters, Sculptors, and Architects:

"Meanwhile, pursuing his amours in secret, Raffaello continued to divert himself beyond measure with the pleasures of love; whence it happened that, having on one occasion indulged in more than his usual excess, he returned to his house in a violent fever. The physicians, therefore, believing that he had overheated himself, and receiving from him no confession of the excess of which he had been guilty, imprudently bled him, insomuch that he was weakened and felt himself sinking; for he was in need rather of restoratives."

But a new study published in the journal Internal and Emergency Medicine suggests that Raphael’s fever was a symptom of pneumonia—not venereal disease—and the doctors’ ill-conceived attempts to treat the infection with bloodletting contributed to his death. Sources from the time state that Raphael had a high, continuous fever that lasted anywhere from eight to 15 days, which a disease like syphilis wouldn’t typically cause.

“A recent sexually transmitted infection—such as gonorrhea and syphilis—could not explain the incubation period,” the study explains. “Similarly an acute manifestation of viral hepatitis could not be considered without jaundice and other signs of liver failure.”

Since there are no records of any typhus or plague outbreaks in Rome from that time period, and because Raphael didn’t appear to have any intestinal symptoms, University of Milan-Bicocca historian Michele Augusto Riva and other authors of the study landed on pneumonia as the most likely culprit. Though 16th-century physicians wouldn’t customarily treat respiratory diseases with bloodletting, it seems that Raphael didn’t give them much information to go on.

“[W]e are sure that bloodletting contributed to Raphael’s death," Augusto Riva told The Guardian. "Physicians of that period were used to practicing bloodletting for the treatment of different diseases, but it would not generally be used for diseases of the lungs. In the case of Raphael, he did not explain the origin of the disease or his symptoms and so the physician incorrectly used bloodletting.”

Draining a patient’s blood while he fights off a high fever seems like a painfully dimwitted idea by today’s standards, but it definitely wasn’t the worst remedy that Renaissance doctors had in their arsenal—read about 11 other wild ones here.

[h/t The Guardian]