Applied Physics

Heat engines transform heat into mechanical energy with the corresponding efficiency of an Otto engine amounting to only about 25 percent, which is what your automobile gets.

The efficiency of heat engines powered by thermal heat reservoirs is determined by the second law of thermodynamics, one of the fundamental concepts in physics. It was as far back as 1824 that Frenchman Nicolas Carnot calculated the maximum possible efficiency limit of such engines, now known as the Carnot limit.

When E. F. Thompson stood on the deck of a ship cruise ship the Indian Ocean in the 1930s and observed a dolphin speed past the vessel in 7 seconds, he had no idea that this single observation would lead Sir James Gray to formulate the enduring paradox that bears Gray's name to this day. 

Based on Thompson's anecdote, Gray estimated the power required to propel the boisterous mammal through the waves at 20 knots (10.3 m/s) and concluded that the animal did not have enough muscle to pull off the feat. Puzzled by the paradox, Gray concluded that dolphins must use a trick of fluid mechanics to sustain the remarkable performance.


What would make snakes scarier?

For spiders, the answer is easy. If you see one big enough to be feasting on Orc flesh in the caves under Mt. Doom, run, but snakes are tougher to make scary because they are slow.

Not all of them. Snakes may not look aerodynamic but some snakes can fly - literally. They slither in air, creating an S shape as they glide as much as 90 feet.

But how do they generate the lift to stay airborne? Jake Socha has spent much of his career figuring out flying snakes and says  "They look like they are swimming. They turn their whole body into one aerodynamic surface."


I was able to find the EYESPY Spydercam at Goodwill. Several hacks for it came to mind, but the simplest is attaching it to a remote control vehicle. I have an old Lego remote control car that’s been gathering dust so I decided to use it for this article. You can, however, attach it to any remote controlled vehicle you may have. I've attached it to the Popular Mechanics RC Tank--hint: use a rubber band to fasten the Spydercam to the battery block. You might not be able to find the RC Tank any more except on eBay. I've also attached it to the Snap Circuits Rover.

Why does beer transform from a liquid to a foamy state after an impact? Science is on the wave propagation case.

As you know, if you shake a carbonated beverage, it will foam over when you open it. But one messy and slightly dangerous bar trick involves hitting a bottle on the opening and watching the base explode. It can happen unintentionally also. Home brewers of beer call this a bottle bomb.


A new battery that runs on sugar has an "unmatched energy density", according to the team behind it.

Other sugar batteries have been developed but energy density has always been the problem. There is a reason gasoline is still popular after 150 years and that reason isn't big oil marketing, it is that the energy density of gasoline is terrific.

The energy density of this new battery is order of magnitude higher than others, allowing it to run longer before needing to be refueled, said Y.H. Percival Zhang, an associate professor of biological systems engineering at Virginia Tech. They believe the technology could progress enough that it could be running in some devices starting in three years. And they could be cheaper, refillable and biodegradable.


Researchers recently got 54 volunteers to try on free shoes. But this wasn't for fun, it was for a biomechanical study of the shoes manufactured by the Majorcan Camper brand.

The six designs of men's and women's footwear were then analyzed using optical motion capture systems, force plates, in-shoe pressure measurement devices and electromyography (EMG) sensors. The aim was to determine the parameters that affect how comfortable the shoes are.
Comic book heroes get into all kinds of crazy situations, everything from alien invaders to losing their powers. Most often, though, might simply makes right -  but what happens when the thing you are fighting gets stronger from being hit? How do you defeat something like that?

It actually happened in "The Mighty Thor" #140 from 1967.

Comics were a lot different in 1967; fantastic, supernatural events were routine plot devices, but even then Marvel was the more 'scientific' of the two large superhero comics companies. Marvel loved genetic mutations and scientists were often heroes or villains but decades ago the resolution of the plot was going to be fast and likely something of a letdown.

Inventor and AC electricity proponent Nikola Tesla was on a mission to transmit energy through thin air almost a century ago, but, claims about a conspiracy to keep his work quiet aside, experimental attempts at the feat have resulted in cumbersome devices that only work over very small distances.

The Toyota Research Institute of North America and Duke University have demonstrated the feasibility of wireless power transfer using metamaterials to create a "superlens" that focuses low-frequency magnetic fields over distances much larger than the size of the transmitter and receiver. The superlens translates the magnetic field emanating from one power coil onto its twin nearly a foot away, inducing an electric current in the receiving coil.


In the comments section of my previous article I demonstrated an optical Theremin. This article is the build for that circuit. The circuit and circuits that are similar to it in function have also been called a “Light Sensitive Tone Generator,” “Photo Theremin,” and “Audible Light Meter.” These three circuits are usually based on the two-transistor Light Sensitive Tone Generator from The Forrest Mims Circuit Scrapbook, Volume 1 (Radio Shack, 1976). The circuit built in this article is based instead on the 555 timer IC.