What are the forces at work here? We have tectonic forces, pushing the pacific plate beneath the island arc of Japan. The weight of the island arc pushes against the subducting pacific plate and creates a resisting, friction force that opposes the tectonic force driving the plates. When all forces are equal, nothing moves. As long as the friction force opposes the tectonic force, the plates will not move. But eventually, the applied tectonic force exceeds the friction force, and the plates move. This movement shakes the crust and releases energy (seismic waves) that travels through the earth. The more sudden and longer the movement, the stronger the shaking/earthquake.
For our "Earthquake Machine," the friction is provided by the brick and the sandpaper. The tectonic force is applied by pulling on the string (which is attached to the spring). The spring transfers the tension to the brick. Once the "tectonic" force exceeds the friction force the brick will slip forward - but only a short distance. The friction causes the brick to slow down and the applied force drops. The spring accumulates some of the tension by deforming (strain), then the accumulated strain can be released. When the spring's force diminishes to that less than the friction force, the brick stops moving; it sticks. The strain on the spring increases again until another slip. This is often referred to stick-slip behavior and is why many active faults don't shake all the time.
The EVATAR is a working model of a reproductive system made from a mouse ovary and bits of a human uterus, cervix, vagina, fallopian tubes, and liver. Developed by Northwestern University researcher Teresa Woodruff and her colleagues, the EVATAR is intended to help better test the effects of medicines and toxins on women. And now […]
Texas State University’s Body Farm (AKA Forensic Anthropology Center at Texas State University or FACTS) is a 45-year-old facility where the corpses of medical body donors are left to decompose so that researchers can observe the rate at which human remains are consumed by the elements, scavengers and microbes, allowing them to accurately date the […]
A better understanding how a sperm swims its way toward an egg could help inform new treatments for male infertility. Researchers from the University of York have now come up with a mathematical formula to model how large numbers of moving sperm interact with fluid they’re swimming through. From the University: By analysing the head […]
Maybe it’s entirely because of podcast ads, but drag-and-drop tools like Squarespace have gotten immensely popular in recent years. While it’s definitely a great tool for any non-coders who want to get a small website up and running quickly, managing content with a primarily visual interface can become a pain once you have more than […]
When you can’t wait for the world’s longest meeting to end, the mindless leg bouncing makes your boredom obvious and just annoys everybody else. Everyone knows the TPS reports need the damn cover sheet, but some sadistic colleague keeps forgetting, probably on purpose just to eat into your lunch hour. Enough is enough!While serving a […]
What could be more fun than a slingshot that shoots tiny airplanes? A slingshot that shoots tiny glowing airplanes of course! These toy planes are outfitted with ultra-bright LEDs, so you can fly all night without losing them in the trees.Whether you are a regular-sized child, or an overgrown adult one, these light-up flyers offer […]