Fun Physics: How to find out if an egg is boiled or raw ?

Without breaking the shell, how can we find out whether an egg is boiled or not ?

Mechanics gives us the answer. The whole trick is that a boiled egg
spins differently than a raw one. Take the egg, place it on a flat plate and spin it (Fig. 39). A cooked egg, especially a hard-boiled one, will revolve much faster and longer than a raw one; as a matter of fact, it is hard to make the raw egg even turn. 

The explanation lies in the fact that while a hard-boiled egg revolves as one whole. In a raw egg - the inside liquid do not rotate with the outside shell and so it puts the brake on the egg's motion. 

Also the boiled and raw eggs stop spinning differently. When you touch a spinning boiled egg with a finger, it stops at once. But a raw egg will continue spinning for a while. The reason for this is "inertia" of the liquid inside the raw egg - the liquid of the raw egg still continue moving even after the solid shell is brought to a state of rest. 

Lyrebird: World's weirdest bird that mimics Chainsaw, Car Alarm and More

Lyrebird is found in Australia

Lyre is a musical instrument of ancient Greece. Lyrebird's spectacular tail of fanned feathers, when spread out in display, looks like a lyre.

Lyrebirds are capable of imitating almost any sound. Mixed in with their own calls, clicks and song, you will usually hear them mimicking loud clear sounds made by other birds and mammals - including humans. They have been heard to mimic the sounds of chainsaws, horns, alarms and even trains. They sing throughout the year, and scientists think that the mimicry helps them to vocally set out their territory and defend it from other lyrebirds.

Video: Lyre Bird sings like a chainsaw! 

Video: Lyrebird mimicking children toy gun and other sounds

Now, it is your turn to find out and share one bird that mimics or makes unique and interesting sounds.

Riddle: Who is the greatest of the gods ?

A king was called "Pharaoh" is ancient Egypt. A Pharaoh asked - 
"Who is the greatest of the gods ?"

"I am not" - said Horus (Horus is a god of the sky and kingship)
"Anubis is" - said Isis (Isis is a goddess of health, marriage, and wisdom)
"Isis is lying" - said Anubis (Anubis is protector of the dead)

The Pharaoh knew that only one of the gods is telling the truth - the other two were lying. Who is the greatest of the gods ?

Robotics: How to water proof electronics

This is a continuation of the hydroplane robotics video.

Robotics: Constructing a hydroplane

Templates (source : http://www.rcgroups.com/forums/thumbgallery.php?t=1647267&do=threadgallery&type=files&group=none&starter=no) 

Micro Photography

Micro photography uses a special "micro" lens that captures finer details of an object.

Try to stand up

You'd think I was joking if I told you that you wouldn't be able to get up from a chair provided you sat on it in a certain way, even though you wouldn't be strapped down to it. Very well, let's have a go. Sit down on a chair in the same way the boy in Fig. 13 is sitting. Sit upright and don't shove your feet under the chair. Now try to get up without moving your feet or bending forward. You can't, however hard you try. You'll never stand up until you push your feet under the chair or lean forwards. Before I explain, let me tell you about the equilibrium of bodies in general, and of the human body in particular. A thing will not topple only when the perpendicular from its centre of gravity goes through its base. 







The leaning cylinder in Fig. 14 is bound to fall. If, on the other hand, the perpendicular from its centre of gravity fell through its base, it wouldn't topple over. The famous leaning towers of Pisa and Bologna, or the leaning campanile in Arkhangelsk (Fig. 15), don't fall, despite their tilt, for the same reason. The perpendiculars from their centres of gravity do not lie outside their bases. Another reason is that their foundations are sunk deep in the ground.


You won't fall only when the perpendicular from your centre of gravity lies within the area bound by the outer edge of your feet (Fig. 16). That is why it is so hard to stand on one leg and still harder to balance on a tight-rope. Our "base" is very small and the perpendicular from the centre of gravity may easily come to lie outside its limits.  Porters who carry loads on their heads are well-built a point, I presume, you have noticed. You may have also seen exquisite statues of women holding jars on their heads. It is because they carry a load on their heads that these people have to hold their heads and bodies upright. If they were to lean in any direction, this would shift the perpendicular from the centre of gravity higher than usual, because of the head-load, outside the base and unbalance them. 

Back now to the problem I set you at the beginning of the chapter. The sitting boy's centre of gravity is inside the body near the spine about 20 centimeters above the level of his navel. Drop a perpendicular from this point. It will pass through the chair behind the feet. You already know that for the man to stand up it should go through the area taken up by the feet. Consequently, when we get up we must either bend forward, to shift the centre of gravity, or shove our feet beneath the chair to place our "base" below.

Do Animals have language ?

All animals communicate. But do they have language? Michele Bishop details the four specific qualities we associate with language and investigates whether or not certain animals utilize some or all of those qualities to communicate.

Riddle: Find logical mistake in the sentence

Mary, in 1925, told her friend, "My husband died in World War I."

Riddle: Color of the bear

If you are sitting in a house with all windows facing south and there is a bear in the window, what is the color of the bear ?

Super heroes of metal world

The word "metal" means strength; but strength can be measured in different ways just like superheroes have different powers.

Malleability

Malleability is the ability of a metal to be hammered into thin sheets. Gold and silver are highly malleable. When a piece of hot iron is hammered it takes the shape of a sheet. The property is not seen in non-metals.

Silver is a transition metal. It has the highest electrical conductivity of any element and the highest thermal conductivity of any metal. The metal occurs naturally in its pure, free form, as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining. It has long been valued as a precious metal

Ductility/Tensile Strength
Ductility is a solid material's ability to deform when it is pulled from both ends; this is often characterized by the material's ability to be stretched into a wire. Again gold is one of the most ductile metals.

Gold - its a very soft and beautiful metal coveted for thousands of years chemical properties of gold.

Hardness
Hardness is a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied.

Titanium is classified as a transitional metal. Titanium is the ninth most abundant element in Earth’s crust. It is almost always present in igneous rocks and their sediments. Pure titanium is a lustrous white metal. It is strong, light with low density, and has excellent corrosion resistance. Titanium is as strong as steel but 45 percent lighter. It is 60 percent heavier than aluminum, but twice as strong.

Toughness
The toughness of a material is the maximum amount of energy it can absorb before fracturing, which is different from the amount of force that can be applied.

Molybdenum is tough metal used in many types of power tools chemical properties of molybdenum.

Corrosion resistance
Corrosion is a process of gradual destruction of metal due to oxygen(process is called - oxidation). 

Zinc is a metallic chemical element. It is the 24th most abundant element in the Earth's crust and has five stable isotopes. Corrosion-resistant zinc plating of steel is the major application for zinc. Other applications are in batteries and alloys, such as brass

Shear strength
Shear strength represents how hard you can try to cut it without it breaking. When you cut a paper with scissors, the paper is failing in its shear strength.

iron is used to make an alloy called "steel" which has very high shear strength. 

How smart are dolphins?

The video below shows bottlenose dolphins' hunting strategy explained in the video above

Video 1 source : ed.ted.com

What is religion ?

What do YOU think a religion is ?

Mouse eating cat

All of the 13 mice in the figure are doomed to be eaten by the cat. But the cat wants to eat them in a certain order. The cat eats one mouse and then counts around the circle in the direction in which the mice are looking. When it gets to 13 it eats the next mouse and starts counting again. Which mouse must the cat eat first so that the white mouse is eaten last?

Source: Fun with Maths and Physics by Perlman 

One word sentences

Certain words in english can be a noun, a proper noun, an adjective and also a verb. Using such words in the same sentence creates confusion in understanding the meaning - this is called "lexical ambiguity". 

'Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo’ is a grammatically correct sentence. How? Emma Bryce explains how this and other one-word sentences illustrate some lexical ambiguities that can turn ordinary words and sentences into mazes that mess with our minds.

How does potato battery work: explanation

Now you have made the potato battery, lets see how it really works. The key concepts are;

• Electrolyte - A medium through which electrons(flow of electrons is "electricity") can travel
• Electrodes 
• Anode - Positively charged electrode, in our experiment Copper is anode
• Cathode - Negatively charged electrode, in our experiment Zinc is cathode

How to make a battery using potato

The Speed of a Train

You are traveling in a train and want to find its speed, could you work it out from the clatter (sound) of the wheels?

Hexaflexagon

Hexaflexagon is a cool little project with paper that all of you will enjoy making.

Watch this video that explains the history of hexaflexagon and also how to make it. Let me know if you find hard to follow this video - I will tell you a trick on how to reduce the speed at which the video plays.

If it was hard to follow the video above, the link below shows step by step method to make a hexaflexagon

http://www.wikihow.com/Fold-a-Hexaflexagon

What is meteor shower ?

A meteoroid is a small body moving in the solar system. This will be called a meteor if it entered in earth's atmosphere - this meteor travels towards earth at 25,000 to 160,000 miles per hour. This meteor becomes brightly visible due to the heat and light it emits at this speed. This light and heat leaves a trail which can be seen in a night sky. This is what many people call "a shooting star" 

When earth passes close to a comet or astroid belt, many such meteors can be seen in the night sky falling at the same time - this is called meteor shower.

Every year in month of August earth passes through the path of a comet called swift-tuttle. This is a best time to watch meteor shower if you are in northern hemisphere.