How Many Triangles ??

Answer : 27

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Physics MCQ's ( Basic + Advance - Must have) Pocket book pdf

Collection of Physics MCQ's ( Basic + Advance - Must have) Pocket book pdf  download now

Click ME to DOWNLOAD(pdf)

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Why does ice float on water ?

"Ice is less dense than water because of its intermolecular forces."

Water contains hydrogen bonds (a type of intermolecular force of attraction) between the H (hydrogen) of one atom and the O (oxygen) of another atom.  As the water gets colder and the kinetic energy of the molecules decreases, the hydrogen bonds keep the water molecules apart, forming hexagonal structures with water molecules at each vertex.  In between the water molecules is nothing.  In liquid water, the molecules of water can be much closer together; the hydrogen bonds are more flexible.  Therefore, the solid ice, with its molecules kept at a fairly fixed distance and the crystals holding lots of "nothing" among the water molecules, is less dense than the liquid water.

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This picture will make you crazy..!!

Some Best Optical Illusions

Want To know about what causes Optical Illusions ?? 

Here is the answer

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Can anything travel faster than light ??

What Travels Faster Than the Speed of Light ??

 

Many people wants to know that ,can anything travel faster than speed of light..?? or simply What Travels Faster Than the Speed of Light ??If you have the same question than here is the answer :

Most textbooks say that nothing can go faster than light, but that statement actually should be qualified: The answer is yes, you can break the light barrier, but not in the way we see in the movies. There are, in fact, several ways to travel faster than light:

1. The Big Bang itself expanded much faster than the speed of light. But this only means that "nothing can go faster than light." Since nothing is just empty space or vacuum, it can expand faster than light speed since no material object is breaking the light barrier. Therefore, empty space can certainly expand faster than light.

2. If you wave a flashlight across the night sky, then, in principle, its image can travel faster than light speed (since the beam of light is going from one part of the Universe to another part on the opposite side, which is, in principle, many light years away). The problem here is that no material object is actually moving faster than light. (Imagine that you are surrounded by a giant sphere one light year across. The image from the light beam will eventually hit the sphere one year later. This image that hits the sphere then races across the entire sphere within a matter of seconds, although the sphere is one light year across.) Just the image of the beam as it races across the night sky is moving faster than light, but there is no message, no net information, no material object  that actually moves along this image.

3. Quantum entanglement moves faster than light. If I have two electrons close together, they can vibrate in unison, according to the quantum theory. If I then separate them, an invisible umbilical cord emerges which connects the two electrons, even though they may be separated by many light years. If I jiggle one electron, the other electron "senses" this vibration instantly, faster than the speed of light. Einstein thought that this therefore disproved the quantum theory, since nothing can go faster than light.

But actually this experiment (the EPR experiment) has been done many times, and each time Einstein was wrong. Information does go faster than light, but Einstein has the last laugh. This is because the information that breaks the light barrier is random, and hence useless. (For example, let's say a friend always wears one red sock and one green sock. You don't know which leg wears which sock. If you suddenly see that one foot has a red sock, then you know instantly, faster than the speed of light, that the other sock is green. But this information is useless. You cannot send Morse code or usable information via red and green socks.)

4. The most credible way of sending signals faster than light is via negative matter. You can do this either by:

a) compressing the space in front of your and expanding the space behind you, so that you surf on a tidal wave of warped space. You can calculate that this tidal wave travels faster than light if driven by negative matter (an exotic form of matter which has never been seen.) b) using a wormhole, which is a portal or shortcut through space-time, like the Looking Glass of Alice.

In summary, the only viable way of breaking the light barrier may be through General Relativity and the warping of space time. However, it is not known if negative matter exists, and whether the wormhole will be stable. To solve the question of stability, you need a fully quantum theory of gravity, and the only such theory which can unite gravity with the quantum theory is string theory (which is what I do for a living). Sadly, the theory is so complex that no has been able to fully solve it and give a definitive anwer to all these questions. Maybe someone reading this blog will be inspired to sovle string theory and answer the question whether we can truly break the light barrier.

 

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What is the speed of electricity?

What is the speed of electricity ?

The speed of electricity really depends on what you mean by the word "electricity". This word is very general and basically means, "all things relating to electric charge". I will assume we are referring to a current of electrical charge traveling through a metal wire, such as through the power cord of a lamp. In the case of electrical currents traveling through metal wires, there are three different velocities present, all of them physically meaningful:

1. The individual electron velocity
2. The electron drift velocity
3. The signal velocity

In order to understand each of these speeds and why they are all different and yet physically meaningful, we need to understand the basics of electric currents. Electric currents in metal wires are formed by free electrons that are moving. In the context of typical electric currents in metal wires, free electrons can be thought of as little balls bouncing around in the grid of fixed, heavy atoms that make up the metal wire. Electrons are really quantum entities, but the more accurate quantum picture is not necessary in this explanation. (When you add in quantum effects, the individual electron velocity becomes the "Fermi velocity".) The non-free electrons, or valence electrons, are bound too tightly to atoms to contribute to the electric current and so can be ignored in this picture. Each free electron in the metal wire is constantly flying in a straight line under its own momentum, colliding with an atom, changing direction because of the collision, and continuing on in a straight line again until the next collision. If a metal wire is left to itself, the free electrons inside constantly fly about and collide into atoms in a random fashion. Macroscopically, we call the random motion of small particles "heat". The actual speed of an individual electron is the amount of nanometers per second that an electron travels while going in a straight line between collisions. A wire left to itself carries no electric signal, so the individual electron velocity of the randomly moving electrons is just a description of the heat in the wire and not the electric current.

Now, if you connect the wire to a battery, you have applied an external electric field to the wire. The electric field points in one direction down the length of the wire. The free electrons in the wire feel a force from this electric field and speed up in the direction of the field (in the opposite direction, actually, because electrons are negatively charged). The electrons continue to collide with atoms, which still causes them to bounce all around in different directions. But on top of this random thermal motion, they now have a net ordered movement in the direction opposite of the electric field. The electric current in the wire consists of the ordered portion of the electrons' motion, whereas the random portion of the motion still just constitutes the heat in the wire. An applied electric field (such as from connecting a battery) therefore causes an electric current to flow down the wire. The average speed at which the electrons move down a wire is what we call the "drift velocity".

Even though the electrons are, on average, drifting down the wire at the drift velocity, this does not mean that the effects of the electrons' motion travels at this velocity. Electrons are not really solid balls. They do not interact with each other by literally knocking into each other's surfaces. Rather, electrons interact through the electromagnetic field. The closer two electrons get to each other, the stronger they repel each other through their electromagnetic fields. The interesting thing is that when an electron moves, its field moves with it, so that the electron can push another electron farther down the wire through its field long before physically reaching the same location in space as this electron. As a result, the electromagnetic effects can travel down a metal wire much faster than any individual electron can. These "effects" are fluctuations in the electromagnetic field as it couples to the electrons and propagates down the wire. Since energy and information are carried by fluctuations in the electromagnetic field, energy and information also travel much faster down an electrical wire than any individual electron.

The speed at which electromagnetic effects travel down a wire is called the "signal velocity", "the wave velocity", or "the group velocity". Note that some books insinuate that the signal velocity describes a purely electromagnetic wave effect. This insinuation can be misleading. If the signal traveling down an electric cable was an isolated electromagnetic wave, then the signal would travel at the speed of light in vacuum c. But it does not. Rather, the signal traveling down an electric cable involves an interaction of both the electromagnetic field fluctuations (the wave) and the electrons. For this reason, the signal velocity is much faster than the electron drift velocity but is slower than the speed of light in vacuum. Generally, the signal velocity is somewhat close to the speed of light in vacuum. Note that the "signal velocity" discussed here describes the physical speed of electromagnetic effects traveling down a wire. In contrast, engineers often use the phrase "signal speed" in a non-scientific way when they really mean "bit rate". While the bit rate of a digital signal traveling through a network does depend on the physical signal velocity in the wires, it also depends on how well the computers in the network can route the signals through the network.

Consider this analogy. A long line of people is waiting to enter a restaurant. Each person fidgets nervously about in their spot in line. The person at the end of the line grows impatient and shoves the person in front of him. In turn, when each person in the line receives a shove from the person behind him, he shoves the person in front of him. The shove will therefore be passed along from person to person, forwards through the line. The shove will reach the restaurant doors long before the last person in line personally makes it to the doors. In this analogy, the people represent the electrons, their arms represent the electromagnetic field, and the shove represents a fluctuation or wave in the electromagnetic field. The speed at which each person fidgets represents the individual electron velocity, the speed at which each person individually progresses through the line represents the electron drift velocity, and the speed at which the shove travels through the line represents the signal velocity. Based on this simple analogy, we would expect the signal velocity to be very fast, the individual velocity to be somewhat fast, and the drift velocity to be slow. (Note that in physics there is also another relevant speed in this context called the "phase velocity". The phase velocity is more of a mathematical tool than a physical reality, so I do not think it is worth discussing here).

The individual electron velocity in a metal wire is typically millions of kilometers per hour. In contrast, the drift velocity is typically only a few meters per hour while the signal velocity is a hundred million to a trillion kilometers per hour. In general, the signal velocity is somewhat close to the speed of light in vacuum, the individual electron speed is about 100 times slower than the signal velocity, and the electron drift speed is as slow as a snail.

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What is electricity and How Electricity is Produced ?

What is electricity ?

Electricity is a form of energy that starts with atoms. You can't see atoms because they're too small, but they make up everything around us. There are three parts to an atom: protons, neutrons and electrons. Electricity is created when electrons move from atom to atom. There are a number of ways to make electrons move, but most electricity is produced at power plants.

How do power plants work ?

Power plants that use water to make electricity are built near rivers.Dams are built across rivers to hold back the water. The water is then directed through big pipes and it falls against the blades of giant turbines. The turbines have blades on them that turn when the water hits them, just like the blades of a pinwheel turn when you blow on them. Once the water hits the blades, it returns to the river.

The turbine blades are attached to a big metal rod, and at the end of that rod are large magnets. When the blades turn, they make the rod and the magnets spin very fast. The magnet end is surrounded by heavy coils of copper wire, and the spinning magnets cause electrons in the wire to begin to move, creating electricity.

What happens to the electricity after that ?

It moves through wires into what's called a power transformer. The electrical voltage (the strength at which electricity flows) is fairly high and the transformer makes it even higher to help it flow through wires called transmission lines. Those wires are attached to wooden or metal poles that you see along roads and throughout communities.

All the wires are made of metal – usually aluminum or copper. That's because metal is a good conductor – electricity travels through it easily. By the way, water is also a good conductor, and because our bodies are mostly made of water, electricity can travel through us easily. That's not something we want to happen though, because if we have electricity going through us we'll likely be seriously hurt or even killed. That's why grown-ups warn you to stay away from high voltage sites and not to stick your fingers in a wall plug.

Electricity travels fast – about 310,000 kilometers per second! If you moved that fast, you could probably make several trips around the world in the time it takes to turn on a light!

Sometimes, when electricity has to travel a long way it gets a little weaker as it moves along the lines. It needs a boost (like you need food to replace the energy you've burned after playing outside all day). That's where substations help. Substations are large box-like power transformers that sit in fenced-in areas. You'll see signs on the fences that say high voltage – stay away and it's really important that you obey those signs (remember what you read about electricity being able to travel easily through your body).

How does electricity get into my house ?

When wires reach your house, another transformer on the power pole makes the electricity just the right voltage so you can use it safely.

The wire is connected to a meter box that keeps track of how much electricity is being used. There are wires in your house connected to plugs, also called outlets. These outlets let you plug in your boom box, television set, or any thing else electrical. What an amazing journey electricity takes to get to your home !!

 

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Nasa has announced that it has found evidence of flowing water on Mars

Nasa Mars water announcement: agency announces it has found proof of flowing water, improving chances of supporting alien life

 

Nasa has announced that it has found evidence of flowing water on Mars — a discovery with potentially huge implications for the possibility of life on the planet.

Scientists have long suspected that the planet might have running water. But the new findings confirm that it is on the planet, combined with “hydrated salts” in a brine.

Normally, water on Mars freezes or evaporates, because of the intense environment on the planet. But the addition of salts means that it is much more stable, allowing it to survive on the Red Planet.

Scientists have long speculated that the Recurring Slope Lineae — or dark patches — on Mars were made up of briny water. But the new findings prove that those patches are caused by liquid water, which it has established by finding the hydrated salts.

The new research is based on an analysis of spectral data from the American space agency Nasa's Mars Reconnaissance Orbiter spacecraft. 

Breaking down reflected light into its different wavelengths provides a chemical "fingerprint" of what a substance is made of. The Mars scientists devised a new method that allowed chemical signatures to be extracted from individual image pixels, providing a much higher level of resolution than had been achieved before.

“Recurring Slope Lineae (RSL) are seasonal flows on warm Martian slopes initially proposed, but not confirmed, to be caused by briny water seeps,” the team behind  the discovery wrote in another paper, due to be delivered this week. “Here we report spectral evidence for hydrated salts on RSL slopes from four different RSL locations from the Compact Reconnaissance Imaging Spectrometer for Mars on board Mars Reconnaissance Orbiter.

“These results confirm the hypothesis that RSL are due to present-day activity of briny water. “

Source:http://www.independent.co.uk/news/science/nasa-mars-water-announcement-agency-announces-that-it-has-found-proof-of-flowing-water-on-mars-a6670446.html

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It is really confusing..3 or 4 ??

Look at the Image you will find it..!!

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New Horizons: New 'treasure trove' of high resolution images show Pluto's surface in greater detail

New Horizons: New 'treasure trove' of high resolution images show Pluto's surface in greater detail

 

New high-resolution images downloaded from NASA's New Horizons probe over 5 billion kilometres away have stunned scientists, revealing Pluto's pitted and cratered surface in even more detail than before.

The New Horizons probe passed Pluto in July, sending back the first close-up images ever seen of the dwarf planet and taking tens of gigabits of data that will take an entire year to send back to Earth.

The latest images now show a range of highly complex surface features, including mountains, deep networks of valleys, nitrogen ice flows and possible wind-blown dunes.

 

Photo: A large region of jumbled broken terrain on the surface of Pluto. The smallest visible features are 0.8 kilometres in size. (NASA/Johns Hopkins University/Southwest Research Institute)

"This is what we came for — these images, spectra and other data types that are going to help us understand the origin and the evolution of the Pluto system for the first time," said New Horizons principal investigator Alan Stern, of the Southwest Research Institute (SwRI) in Colorado.

"And what's coming is not just the remaining 95 per cent of the data that's still aboard the spacecraft — it's the best datasets, the highest-resolution images and spectra, the most important atmospheric datasets, and more. It's a treasure trove.

"Pluto is showing us a diversity of landforms and complexity of processes that rival anything we've seen in the solar system.

"If an artist had painted this Pluto before our flyby, I probably would have called it over the top — but that's what is actually there."

The revelation of possible dunes on the dwarf planet's surface has also piqued scientists' interest, as they indicate the atmosphere would have had to be thicker for wind to create the formations.

Timelapse: Pluto comes into focus

View an interactive timelapse of Pluto images captured by New Horizons, and find out what they tell us about this icy dwarf planet.

"Seeing dunes on Pluto — if that is what they are — would be completely wild, because Pluto's atmosphere today is so thin," said William B McKinnon, a GGI deputy lead from Washington University.

"Either Pluto had a thicker atmosphere in the past, or some process we haven't figured out is at work. It's a head-scratcher."

The images have more than doubled the amount of Pluto's surface, seen at resolutions as good as 400 metres per pixel.

They have also revealed Pluto's global atmospheric haze has more layers than scientists realized, creating a twilight effect that softly illuminates nightside terrain near sunset, making it visible to the cameras aboard New Horizons.

"This bonus twilight view is a wonderful gift that Pluto has handed to us," said John Spencer, a GGI deputy lead from SwRI.

"Now we can study geology in terrain that we never expected to see."

The discoveries made from the new imagery will not be limited to the dwarf planet itself — better images of Pluto's moons Charon, Nix and Hydra are also set to be released.

Photo: An image of Pluto's surface showing a smooth ice plain informally dubbed Sputnik Planum. (NASA/Johns Hopkins University/Southwest Research Institute)

 

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