How is it possible to lie without harm on a bed of nails?

We know that pressure is a force divided by area over which the force is exerted. When a person lies on a bed of nails, the force equal to the weight of that person acts on the surface of the bed containing nails. Here, the weight is distributed over hundreds of nails that makes the pressure at the tip of each nail safely small. If the same person stands on his feet, he will surely feel the sharpness of the nails because in this case the area of  contact is very small. So, the weight will be distributed over a few nails and hence the pressure will be relatively large.   

What is the reason of cooler air coming out of a bursting tire?

We know from the ideal gas law that pressure increases proportionally with the increase of temperature when volume is held constant for a given mass. As the air inside the tire is in compressed state, the temperature inside the tire is high. When the tire bursts, air inside the tire comes out very fast causing a sudden expansion and decrease in temperature. Therefore, the air is relatively cooler than the surroundings. Blowout of tire occurs when the location of tearing of the tire is incapable of containing the pressurized air and the escaping air causes further tear of the tire.

How glass is broken with sound?

When any object composed of an elastic material is disturbed, it will vibrate at its own special set of frequencies, which together form its special sound.The frequency is the natural frequency of that object. The tendency of one object to force another object into vibrational motion is called forced vibration. If an unmounted tuning fork is struck, the sound it makes is faint. Hold the base of the fork on a table top, and the sound is relatively loud. This is because the table is forced to vibrate, and its larger surface sets more air in motion. The table top becomes a sounding board, and can be forced into vibration with forks of various frequencies. When the frequency of forced vibrations on an object matches the object's natural frequency, a dramatic increase in amplitude occurs. This phenomenon is known as resonance. A glass has a natural frequency. Now if the pitch of the sound creating forced vibration match the resonant frequency of glass the vibrating air will cause the glass vibrating too. If this occur with sufficient volume, right frequency and high enough amplitude, this will cause exceed the strength of the glass to resist the vibrations. When the sound gets too loud for the glass to vibrate, it breaks the glass.  

Why do astronauts float in the space station?

SCIENCE FACTS(Astronaut)

Weightlessness in an orbiting spacecraft is physically identical to free-fall.An object that rests on the ground is subject to a normal force exerted by the ground. The normal force acts only on the boundary of the object that is in contact with the ground. This force is transferred into the body.The force of gravity on every part of the body is balanced by stress forces acting on that part. A weightless astronaut feels weightless due to the absence of these stress forces.But actually they are not weightless.It is gravity that keeps the space station, the astronauts, and their equipment in orbit around the Earth.An object in orbit around the Earth is falling with sideways motion that is so rapid that as it falls, the Earth’s surface moves away at just the right rate that it falls around the Earth.This is exactly what the Moon is doing in its orbit around the Earth. It is falling, but moving sideways so rapidly so that instead of approaching the Earth’s surface, it remains at an approximately fixed distance.Inside the station,astronauts and their equipments float because they and their equipments are falling — falling around the Earth — along with everything inside their spacecraft.If we look at them from outside their spacecraft,we can see they are not floating and traveling in a circle around the Earth.But inside the space station,they appear to be floating,and they experience weightlessness.
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Sonic boom

Do you know what is sonic boom?

SCIENCE FACTS(Sonic boom)

When an object traveling through the air faster than the speed of sound,it creates such a strong shock wave that it is heard on ground as a sonic boom.Sonic booms produce abundant amounts of sound energy.Sonic boom is associated with shock wave.The shock wave starts at the nose of the aircraft and ends at the tail.When a supersonic aircraft creates a series of pressure waves in front of it and hitting the waves in front before they cannot get out of the way of each other,the successive waves are forced together or getting mixed up.This is how sonic boom is created. Longer aircraft spread out their booms more than smaller ones, which leads to a less powerful boom.

Glass

How can we see through glass?

SCIENCE FACTS(Glass)

Glass is a transperant object which is an amorphous(non-crystalline) solid. The primary constituent of glass is sand(silicon dioxide,SiO₂).The atoms in a solid are tightly bound to each other.The molecules are held together with strong intermoleculer force.Therefore the molecules can not move freely and the space between them is very little.So,they do not allow light to pass through them.Light can pass through liquids and gases because the molecules of liquids and gases can move freely and a lot of space between them.Glass is manufactured by melting sand at a very high temperature and then cooling it.Therefore brittle substance is produced but glass still contains the free moving molecules of a liquid.So,light can pass through the free space between the molecules although glass itself is a solid.

Why does sun glow?

SCIENCE FACTS(Sun)

The Sun is the star at the center of the Solar System and composed of helium and hydrogen.Sunlight is the main source of energy for life on earth.Nuclear fusion at the core of the Sun produces an appreciable amount of thermal energy that makes the Sun glow.The interior of the Sun is radiative and nuclear fusion in the inner portions of the Sun has modified the composition by converting hydrogen into helium.The reactive core zone where hydrogen is converted into helium, is starting to surround the core of helium ash.This will continue and cause the sun to become red giant.This nuclear fusions produce thermal energy and that same energy reaches us as heat and light.Sunlight is mainly composed of infrared light,visible light and ultraviolet light.