Why does a steel ball pitch higher than a rubber ball?

It is a scientific fact that the height to which any object bounces depends on its elasticity. This physical property is defined as the ratio of stress (The force acing on a unit area of the ball during compaction) created on the object to the strain (change in size of the ball) which acts on it. It is independent of the density of the material.

For larger values of elasticity, the strain should be smaller for a given amount of stress. In the case of a steel ball and a rubber ball, though steel has higher than rubber, it has greater elasticity, as the strain produced in steel is much less than that in rubber, for constant stress. In the case of a bouncing steel ball and a rubber ball, even though steel has higher density          than rubber, it has greater elasticity, as the strain produced in steel is much less than that in rubber, for constant stress. In the case of a bouncing steel ball, collision is elastic in which both momentum and kinetic energy are almost conserved.



            That is, the energy loss is minimum. Hence the steel ball bounces to a greater height than the rubber ball.



 


How is information stored in audio and video tapes?

Information is stored in audio/video tapes by magnetizing them. These tapes are actually long, thin plastic films coated with a magnetic material, mainly iron oxide.

Likewise, the player has a recording head which consists of a coil of a wire wound around a circular piece of iron with a small gap. Any current passing through the wire would produce a magnetic field around it.



Information (voice or image or any data) to be stored is converted into electric signals (by a microphone) amplified and fed to the recorder head. As the current varies in accordance with the image or sound (input signals) to be recorded, it produces a varying magnetic field.



When the tape is run through the small gap present in the recording head, the varying magnetic field magnetizes the particles on the tape rearranged their moments in accordance with the variation in the input signal.



To reproduce the signal recorded, the tape is again run past the recording/playing head which   senses the magnetic field along the tape. This induces a varying current in the coil. This current is amplified and fed to the speaker or TV to reproduce the original message.


What is the origin of gravity?

For a long time people have wondered what makes the planets go round the Sun and why anything thrown up comes down. Sir Isaac Newton probed the origin of this mysterious force and gave us the law of gravitation.

According to the law, which we have learnt in school, the force acting between two objects depends on their masses and the distance between them.



  The law makes it clear that the origin of gravity is the object itself- that is, by virtue of its own mass any object will have an influence on another object (mass). But if one were to ask why an object (mass) should exert a force on another, our present scientific knowledge does not provide a clear answer.



It seems that even Newton had thought about this question and tried in vain to get an answer. Finally he too admitted it is a god-given property to all objects.



               


What is brake horse power (BHP)? How is it different from the horse power (HP)?


 



 



 



 



 



 



 



 The term horse power was introduced by James Watt. He chose a normal horse and found that it could do a work of 33,000 ft-lb in a minute. He adopted this measure for comparing the performance of his engines.



  The actual power generated in the engine cylinder is called the indicated horse power (IHP). It is also defined as the power fed into the engine in the form of steam or calorific value of the fuel.



But all that power is not available to do useful work. This is because, part of it is used to overcome internal friction of the moving parts of the engine, work of charging, air resistance to flywheel rotation, and drive auxiliaries such as fuel pumps, governor, lubrication oil and water circulating pumps. This net power output of the engine is called brake horse power (BHP). It is 15- 30 per cent less than IHP.



The term brake horse power comes from the braking device used to measure the power output by stopping the engine.



 Thus it is the amount of power that the engine can produce at a certain speed (measured as rotations per minute).



Usually engines are rated with the help of dynamometers. The device has a power absorber, such as an electric generator or a water brake, which can put different loads on the engine. 


We are all familiar with the popping ears associated with takeoff and landing in an aero plane. This is caused by changes in pressure, but because the aircraft cabin is artificially pressurized, why i

For reasons of fuel economy, large civil transport aircraft have to fly at altitudes far in excess of those capable of sustaining life. Whereas 5,500 m is about the maximum altitude at which a person can live for any extended period, a subsonic passenger jet has the best fuel economy when flying at around 12,000 m.

Aircraft manufacturers therefore, have no choice but to pressurize the interior of a passenger aircraft. This poses huge technical problem. At 12,000 m, where the pressure is about one-fifth of that at sea level, the pressure inside is trying to burst the fuselage apart. This pressure has to be contained and all the stretching and flexing of the fuselage during a flight has to be kept within safe limits.



It is far easier to do this - if the pressure differential between inside and outside is kept to a minimum, a cheaper and lighter fuselage structure can be used.



For civil airliners this means that the pressure inside during cruising is kept at the lowest possible safe level - 2500 m. This is about the maximum altitude which a normal healthy person can be subjected to without ill effects.



 Even so, unfit people, those with respiratory illness and those who have sampled a few too many duty-free drinks might still feel ill, even at this altitude.



There is another problem: all airfields are not at the same altitude. In an extreme case, a flight from Heathrow in England to La Paz in Bolivia would entail going from sea level to around 5200 m, where the air pressure is about half that at sea level. Under these circumstances it is just not possible to maintain the same pressure throughout the flight. Imagine what would happen if the pressure inside and outside were not the same at the time the doors were opened: the effect would be quite spectacular and most undesirable.



As for the ear popping, nowadays, for your safety and comfort the internal pressure is imperceptibly reduced, all under computer control, as the aircraft climbs. It is gradually increased during descent so that, as the aircraft is coming to a stop on the runway, the pressure inside and out is the same. This is normally sufficient for your ears to adjust, but if all else fails, pinch your nose and gently but firmly increase the pressure in the nasal cavity until you feel the pressure equalize.



 


Why does a spinning top reverse its direction of rotation towards the end?


A spinning top process (or rotate) about its central axis due to the lateral forces given initially or due to lack of speed (as during the end of spinning). When the speed becomes too low (not zero) for it to hold it (its mass) upright, it falls down.



 As the body of the top touches the ground, due to friction it is unable to spin and so the remaining spin (force) forces it to roll on the ground, obviously in the opposite direction.



 Due to tapering shape of the top, it tends to rotate along a circle in the reverse                                                                                             direction, with the nail pointing towards the                                                                                    centre.


While light from a candle illuminates a room, the gas (LPG) flame does not. At the same time the gas stoves help cook faster. Can anyone explain?


Combustion (burning of fuel) can be classified into two: complete and incomplete.



 Combustion of the fuel will be complete when there is sufficient quantity of oxygen for the fuel to burn. These results in a blue flame and the heat generated will be maximum. Combustion is termed incomplete when the oxygen supply is insufficient. This results in a yellow flame. As a result, the heat produced is lesser than the maximum obtainable from the fuel.



In the case of a candle flame, as one can see, there are three distinct zones. The hottest zone surrounding the wick is blue in colour. A zone of unburnt volatile fuel forms the centre of the flame. The yellow luminous zone which is responsible for illuminating the room forms a major portion of the flame. This zone contains hot carbon particles which get heated by hotter zone below. They emit light due to incandescence. As they move out of the flame and escape into the air, they get oxidized and cooled. The process continues as more fuel is burnt.



In the case of LPG (liquefied petroleum gas, which is mostly propane and a little butane), the aim is to get the maximum heat energy from the fuel so that the cooking time is reduced and fuel conserved. Hence the incoming gas is mixed with sufficient quantities of air in the burner and then burnt to give a blue flame.



It is known that propane needs about 25 times its volume for complete combustion. Hence by designing the pinhole (which lets the gas into the burner) suitably, the flow of gas is controlled and ratio of gas and air is maintained. As there is no incandescent zone the flame does not illuminate the room. But, sometimes we see that dust and rust block the holes preventing free flow of air. This results in a yellow flame which illuminates the room just like the candle flame.



Also in the case of LPG stoves, as all the fuel that is injected is burnt fully, the heat generated is more and the cooking time is reduced.



                    


What is the difference between hydrogen and an atom bomb?


 



 



 



 



 



 



 



An atom bomb is a fission device. Here a heavy atom (such as uranium) is split into two or more lighter atoms. In such a nuclear fission process, one or two neutrons are also released from each atom. If these neutrons are captured by the surrounding heavy atom, further fission takes place leading to further neutron release. In atomic power reactors, this chain reaction is controlled so that the energy released during the reaction can be used beneficially.



But in the case of an atom bomb, the chain reaction is not controlled but left free. This leads to the release of large amounts of heat energy in a very short time resulting in a catastrophic explosion.



In a fusion bomb, such as the hydrogen bomb, two or more lighter atoms fuse together to form a heavier atom. Such fusion reactions can take place only at very high temperatures; say a few million degrees Celsius.



Only at such temperatures can the starting atoms overcome the repulsive forces acting between them.



 In this case also, when uncontrolled fusion takes place a large amount of energy is suddenly released resulting in an explosion far bigger than an atomic explosion.



 It may be noted that the temperature needed to initiate a fusion reaction is normally obtained by a fission reaction.


Why does boiling milk overflow but boiling water does not?


            The major component of milk is water (83-87%). Its other constituents are protein (3.5%), sugar (5%) and fat (4-7.4%). When heated, fat being lighter than water, floats as a creamy layer on the top and water vapour, in the form of steam bubbles, is trapped under it. Further heating results in the formation of more number of bubbles. These bubbles expand and lift the creamy layer causing it to overflow. In the case of water, the steam bubbles break as                                                                                          they reach the surface.


How do hearing aids work?


 Hearing aid is an electronic device used by those who are hard of hearing, to amplify sounds particularly speech. It’s essential components are a microphone, an electronic amplifier and a receiver, all operated by a battery. In simple terms, the hearing aid can be likened to a miniature public address system. Sounds are amplified by the amplifier and the output is fed to the receiver.



The gain and amplification of the device is determined by the amplifier. In fact, there are low gain, moderate gain and high gain hearing aids. We know that sound signals are wave patterns in which air molecules vibrate, and waves representing different sounds differ in their wave length (and frequency).



As the human ear can selectively respond to certain frequencies very well and not so well to others, manufacturers vary the frequency response of hearing aids with electronic filters, based on the audiometric configurations (low frequency, high frequency or flat loss of hearing) of the user.



Externally most of the aids are provided with a battery compartment, on- off switch, tone control (to adjust the frequency response) and a volume control (to adjust amplification).



In some aids the on-off switch will be provided with a telephone setting to enable the individual to use the telephone. This is made possible with a telecoil in the aid which selectively picks up telephone signals.



                             


What is Global Positioning System (GPS) and how does it work?


GPS is a system which shows the exact position on the earth, anytime in any weather and anywhere. There are 24 GPS satellites orbiting at 11,000 nautical miles above the earth. They are continuously monitored by ground station located worldwide. The satellites transmit signal that can be detected by anyone with a GPS receiver. Using the receiver one can determine the exact position namely longitude, latitude, altitude and the time, with greater precision. GPS has 3 parts: the space segment, user segment and the central segment.  Space segments consists of 24 satellites as stated above. User segment consists of receivers which we can hold in hand or mount in a car and this gives the exact location on the earth. The control segment consists of ground stations that make sure that the satellites are working properly.



The satellites are equipped with precise clocks that keep accurate time to within 3 nano seconds (3x10-9 secs). The time signals are transmitted along with their orbital parameters. The receiver detects the time signal and calculates the distance of the satellite. By getting the signals from three different satellites and by doing mathematical calculations, the receiver is able to give the exact position where the receiver’s located. By getting the information from fourth satellite, it is able to give the time also.



Thus four satellites are required to compute the four dimensions of x, y, z (position) and time. At any time and at any location always a minimum of four satellites will be visible for the receiver.



Global Positioning System (GPS) works on set of navigational satellites (18 to 21 nos) around the earth in orbit and their signals to a receiver on earth. The signal from each satellite provides the position of the satellite at a specific time.



The receiver software analyses the signals and displays the position of the receiver with reference to a specific spherical coordinates, which has, its centre of earth as its origin.  The navigational satellites are so orbiting that at any given time and spaces on the earth, a minimum of three are visible to the receiver. 



 The accuracy of the position increases with the number of satellites the positional accuracy is around 200 NV, with a different correction (a method of using two or more receiver) the accuracy can be increased to centimetres. Ifs are has been increasing since Iraq war, especially in all modes transportation.  



The Global Positioning System is a satellite based Radio Navigation System developed by the United States Department of Defence. It provides continuous, all weather worldwide navigation capability for sea, land and air applications.



The user can easily determine his position, i.e. latitude, longitude and altitude using the GPS receiver which receives signals from various satellites orbiting the earth. 'Tie complete GPS constellation consists of 21 operational satellites and 3 spares, orbiting the earth about once every 12 hours at a distance of roughly 10,900 nautical miles.



 Unlike ground based navigational system signal generators the satellites are able to cover a very large area of the earth because of their altitude and the fact that their signals are free of interference from local geography. The error in GPS at times may come up to 30 to 100 Mts.



An advanced system known as GDPs or differential Global Positioning System evaluates this error with an accuracy of within 5 Mts.


Why does not sound travel in vacuum but light does?


The basic difference between a sound wave and a light wave is that the former is a mechanical wave while light is an electromagnetic (EM) wave. Mechanical propagate by the actual displacement of physical particles. Each particle oscillates about its mean position in a synchronized manner to cause energy propagation in a mechanical wave pattern. In case of EM waves, electric and magnetic fields ‘oscillate’ about their mean zero in mutually perpendicular planes and cause wave motion. Mechanical waves require particles to oscillate and enable it to move on. Hence, they require some medium (to provide these particles) for travel. EM waves consist of only change in electric and magnetic fields. So, they do not need any medium for propagation.


Why is it possible to hear noises from far away clearly on cool damp evenings? Is it because sound travels better in cool, damp air than in dry air?


The most likely explanation for this phenomenon is that warm, damp air at ground level was sitting below a layer of drier, hotter air above. This results in refraction of the sound back down towards the ground and also the unusually high propagation distances - you hear sound which, under normal circumstances would pass over your head.



Also another explanation could be that sound travel better at night, but the reduction of daytime noise means that continual sounds become more apparent. In the evening it is usual for the temperature near the ground to fall more quickly than that higher up, causing a temperature inversion. It is not uncommon for there to be a change in the air’s moisture content at the top of this inversion layer.



The change in temperature and moisture lead to a density discontinuity which refracts sound waves much as the refraction of light causes a mirage. Sounds are trapped near the ground rather than dispersed. The wind speed in this low-level inversion layer is also normally lighter and this adds to the effect.


Why do we not hear sound while sleeping or meditating?


Sleep does not reflect an inactive brain and so we do hear sound while sleeping.  It is a recurrent healthy state of inertia and reduced responsiveness found among higher vertebrates. It is controlled by the brain and is associated with characteristic electrical rhythms in the brain. Sleep is induced when the central core of the brainstem situated below the cerebral hemisphere is stimulated. Stimulation of the reticular formation (portion of the central nervous system which consists of small islands of gray matter separated by fine bundles of nerve fibres running in every direction) by natural sensory input, by messages from the cerebral cortex can awaken sleeping persons.



 Neurons (nerve cells) in REM sleep are as active as they are in wakefulness. Mental capacity also does not decrease. Incoming sounds are subjected to ceaseless scrutiny. Unimportant sounds are ignored but important ones even if feeble cause arousal. Arousal thresholds are variable and they are a function of the meaningfulness of the stimulus.



 With a stimulus having no significance, to the sleeper, thresholds can be rather high. So irrelevant stimuli are actively shut out during REM. Behaviourally, it has been established that motor responses can be evolved in all stages of sleep, but it is difficult to demonstrate that new responses can be acquired during sleep. But, in meditation man achieves a state of rest deeper than sleep indicated by slower heartbeat and breathing and so we do not hear sound. 



 


Why does the flow of ink increases when pens are about to run out of ink?


When the pen is full of ink, there is very little space for air inside the pen. So while writing the ink gradually oozes out through the cut in the nib. This leads to a very weak vacuum inside the pen. So the outside air tries to enter the pen and holds the ink from flowing out freely. This ensures a smooth flow of ink.



As the ink runs out and when there are only a few drops of ink the air column inside the pen is no longer isolated from outside the air. Hence the outside air can enter the pen freely and there is no difference in air pressure. Thus the force acting on the ink will be only the gravitational pull and so the ink begins to drain out.