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Why is it easier to fly a kite with a tail?

A kite flies better without wobbling, spinning or diving if it can keep itself inclined at a specific angle against the blowing wind. This creates a difference in the air-pressure around the kite in such a way that the kite is lifted up. The tail helps a kite in keeping its angle of inclination stable by pulling down its lower tip. Without the tail, wind blowing against the kite and the lift-force generated in turn would send a conventional kite into a tail-spin. Box-kites, however, do not need a tail to stabilize as they do not need to maintain a constant facing angle against the wind to generate the lift. The air swirling through and about a box-kite creates all the pressure differences required to lift up.

How do CDs and DVDs store information?

On the surface, both CDs and DVDs are alike. They are round in shape and have a shiny surface on the underside. In both DVDs and CDs, data is stored in microscopic tracks that are made up of ‘pits’ which are grooves and ‘lands’, which are flat surfaces, backed by the shiny, reflective When the player spins the disc, a laser beam shines on these pits and lands. The reflected light patterns are then read by an optical device. This device converts the patterns into little bits of data called, appropriately enough, bits. The bits are assembled into bytes that can in turn represent just about any kind of data imaginable, which includes text, sounds and A DVD has smaller pits than a CD in different vertical layers. A DVD has a much larger data capacity. A standard DVD holds about seven times more data than a CD DVD picture quality is better than that on a CD, and many DVDs have Dolby Digital or DTS sound, which is much closer to the sound you experience in a movie theatre.

What are smart cards?

You must have seen people using credit cards in shops. A smart card resembles a credit card in size and shape, but the inside, it is completely different. First of all, a normal credit card is a simple piece of plastic, but the inside of a smart card usually contains what is called a microprocessor. A microprocessor is the heart of any normal computer, and has the ability to store and update information. Smart cards have many uses in credit cards, ATMs, banking, identification, mobile phones, etc, to name just a few. The microprocessor in the smart card is there for security, and this is one of the greatest advantages of using smart cards

What is the role of computers in communication?

Computers play an important role in communication. Large companies use a network of computers to run their business. When people cannot meet in person to discuss matters, they can use video conferencing to share ideas even if they live in different continents. Video conference is a system where computer networks, telephones and video cameras are used to let people see and talk to each  E-mail is also an important tool of communication if you have a computer and an internet connection. E-mail is nothing more than sending and receiving messages through your computer. People use e-mail for business, to keep in touch with friends and relatives, and to work on a project with someone a hundred kilometres away. The internet is also used for communicating in chat rooms and newsgroups. You can chat with a friend who is far away by typing or even speaking to him as you would do with a  New ways of using computers for communication are being developed at a fast pace. In addition to using videophones to speak to, and see people for way, cars can now find routes to avoid traffic jams, and even give you directions to reach a particular place. ships and trains, planes and spaceships, all depend on computers in one way or the other

What are the uses of the internet?

Did you know that your computer can be connected to another computer in Africa or America? This is possible because of a giant network called the internet that connects computers through phone lines, cable and satellite links. If you take an internet connection, your computer becomes a part of this network.  An internet connection will allow you to communicate with other users all over the world through electronic mail or email. You can also get access the World Wide Web, which is a vast store of information. You can download this information on to your own computer, copy it and print it. The World Wide Web has many sites that give you news and entertainment too.  So, we can say that the three main uses of the internet are communication, research and ‘publishing’ on the World Wide Web. The Web allows for the display of still images, moving video, audio and text in any combination. The fact is that once you start using the internet, you will find that ‘browsing’ or ‘surfing’ the internet is a very good way to learn a lot… and have a lot of fun as well, for you can play many exciting games on the internet

Why does the second hand of a quartz clock move in jerks?

            The seconds hand of both quartz and spring watches move in jerks. Only the movement is much more discernible in quartz watches. In spring watches the movement of the seconds hand is guided by the oscillations of the balance-wheel driven by the hair spring. Since the balance wheel oscillates several times a second, the seconds hand in a spring watch appears to move smoothly as the small jerks are almost non-discernible. On the other hand, in quartz watches, the battery powers a stepping motor that moves the second hand in a single step once every second, which can be quite easily made out and the movement appears jerky.

        Another reason for the illusion is the difference in the amount of angular movement each jerk produces in a second hand. In spring watches it is only  whereas in quartz watches it moves by as much as  in a single step.

                                     

Why doesn’t soap form lather in hard water?

   Soaps are salts of fatty acids. Common soaps are water soluble sodium and potassium salts of fatty acids. Soap cannot form lather unless it dissolves in water. Hard water does not dissolve soap because the calcium and magnesium salts present in it produce insoluble substances by reacting with soap. These insoluble substances separate out as scum and reduce the effectiveness of the soap as a cleansing agent.

What are the common gestures used by Americans?

When greeting one another, Americans shake hands. From an early Americans are taught to shake hands with a firm solid Other commonly used gestures include signaling goodbye by waving the hand and beckoning someone with a curving motion of the index finger. Nodding the head means ‘yes’, shaking it from side to side means ‘no’.A palm facing outwards with the middle finger and index finger forming a ‘V’ and the other fingers clenched signifies ‘victory’ or ‘peace’. You can say ‘OK’ by forming a circle with your thumb and forefinger, while a closed fist with the thumb up means ‘good job!’ Like us, the Americans to extend the forefinger and make a circling motion near the forehead to say ‘he’s crazy’!