FORCE AND MOTION

Forces are pushes or pulls that change the motion of objects. To make a stationary object move, or a moving object stop, a force is needed. A force is also required to change the speed or direction of an object. This change in speed or direction is known as acceleration. Acceleration depends on the size (magnitude) of the force and on the mass of the object. The effects of forces were first summarized by Isaac Newton in his three laws of motion. the international unit of force, named after him, is known as newton (N), which is approximately equal to the weight of one apple. Gravity-the force attraction between any two masses can be measured using newton meter (spring balance). Forces are put to useful effect in machines. A simple machine, such as a wheel and axle, is a device that changes the size or direction of an applied force. It allows an applied force (the effort) to produce another force (the load). A lever uses a bar that turns on a fulcrum to exert force. In all simple machines, there is a relationship between force and distance. A small force (in a compound pulley, for instance) moves through a large distance to lift a heavy object a small distance. This is called the Law of simple Machines.

VAN DE GRAAFF GENERATOR, ITS PRINCIPLE,CONSTRUCTION AND WORKING.

V a N      d E     G r A a F f     G E n E r a T O r

A Van de Graaff  generator is a device designed to create static electricity and make it available for experimentation.
  
                      The American physicist Dr. Robert Jemison Van de Graaff invented the Van de Graaff generator in 1931. The device
has the ability produce extremely high voltages as high as 20 million volts. Van de Graaff invented the generator to supply the high energy needed  for early particle accelerators. these accelerators are known as atom smashers because they accelerate the sub-atomic particles to very high speeds and then "smashed" them into the target atoms. The resulting collisions created other subatomic particles and high energy radiation such as X-rays. The ability to create these high-energy collisions in the foundation of particle and nuclear physics.


PRINCIPLE:

The Van de Graaff generator works on the following two principles.

1. Discharging action of sharp points i.e., electric discharge takes place in air or gases readily at pointed conductors.
2. If the charged conductor is brought into internal contact with a hollow conductor , all of its charge transfers to the surface of the hollow conductor  no matter how high the potential of the latter may be.

CONSTRUCTION:

M- a large spherical conducting shell is supported at a height several meters from the ground on an insulator column.

B- an insulating belt wound around two pulleys P1 and P2, this belt is moving continuously by a driven motor at constant speed.

C1,C2- sharply pointed combs close to the belt near its bottom and top, C1 has given 10kV by a high-tension battery (HT) and termed as spray comb and C2 is connected to spherical shell and termed as collector comb.

WORKING:

The high electric field at the pointed end comb C1 ionises the air near them. The +ve charges in air are repelled and got deposited on the belt through a corona discharge. The charges are carried upto C2. A similar corona discharge takes place at C2 and the charges are finally transferred to the shell M. The charge spread over uniformly on the outer surface of M raising its potential to few million volts.

FTP (File Transfer Protocol) AND IT'S ADVANTAGES

FTP is a convention or set of rules used for transferring files from one computer (or network) to another computer (or network). Thus FTP allows copying of files from a remote server to our own computer and transferring files from our computer to some remote computer. Using FTP a user can log on to a remote computer by giving the address of the host computer.

Besides managing the access control and file transfers, FTP also deals with protection given to a file. Protection may not be given to a file if it is assumed that all the clients are trustworthy. Whenever the clients make requests, the server provides the requested files as they are.

A second alternative is to assign a password to each authorized user. The server, before giving access to any file, will check the password of the client and process his/her request only if the password is valid. A third alternative is assign a password to the files. The passwords assigned for files provide different access rights such as read only, modification and full control.


ADVANTAGES OF FTP :

• Useful for transferring files from one network in an organization to another.
• Geographically separated groups working on a common project may co-operate and co-ordinate with each other.
• Most useful way of sharing information and resources over WANs like internet.

 

URL (Universal Resource Locator)

The function of the web server hardware and software is to store the web pages and locate and transmit them to a client computer as and when requests for the web pages come in. When we want to download a website, its address is to be specified at the concerned prompt in the browser program. the web site address is called Universal Resource Locator (URL), which is the address of the home page of the website installed on the web server. There is standard format for the web sited address. It has generally  three parts (eg  www.abcd.com) where www is based on the HTTP, the recent addition to the TCP/IP protocol suite; abcd represents the name of the site; and com is the domain name that describes organizational or geographical realities like com, org,  in, au, etc

RADIO WAVES

R a D I o    W a V E s


Radio waves belongs to the unguided media and they are of different frequencies ranging from 3 KHz to 300 KHz. The picture below shows the spectrum of the radio communication band.

• Very Low Frequency (VLF) waves propagate s surface waves, usually through air, but sometimes through water also. They are usually used for long rang radio navigation and submarine communication.

• Low Frequency (LF) waves also propagate as surface waves and these are used for long range radio navigation or navigation locators.

• Middle Frequency (MF) waves reply on line of sight antennas to increase and control absorption problems. These waves are used for  Am radio, radio direction finding and emergency frequencies.

•  High Frequency (HF) waves are used for amateur radio, international broadcasting, military communication, telephone, telegraph and facsimile communication.
• Very High Frequency (VHF) waves use line of sight propagation and are used for VHF television, FM radio, aircraft AM radio and aircraft navigation.

• Ultra High Frequency (UHF) waves use fine of sight propagation and they are used for television, mobile phone, cellular radio, paging and micro wave links.

• Super High Frequency (SHF) waves are transmitted as either line of sight or into space. They are used foe terrestrial and satellite microwave and radar communication.

• Extremely High Frequency (EHF) waves are transmitted into space, and are used for scientific applications such as radar, satellite and experimental communication.

WEB PAGE

W e B    P a g E



A web page is a simple text file that contains not only text but also a set of HTML (Hyper Text Markup Language ) tags that describe how the text should be  formatted when a browser displays it on the screen. The tags are simple instructions that tell the web browser how the page should look when it is displayed. The tags tell the browser to do things like  change the font size or colour or arrange things in columns. A web page can contain, text, graphics images or even animated graphics. the web pages are created with the HTML language and stored in a computer file having .html or .htm extension in the file name. The extension identifies the file as an HTML file.

MOUNTAIN BUILDING

M o U N t A i N     B u i L D i n G

The process involved n mountain building-termed orogenesis  occur as a result of the movement of the Earth's crustal plates. There are three main types of mountains: volcanic mountains, fold mountains and block mountains. most volcanic mountains have been formed along plate boundaries where plates have come together or  moved apart and lava and other debris have been ejected onto the Earth's surface. The lava and debris may have built up to form a dome around the vent of a volcano. Fold mountains are formed where plates push together and cause the rock to buckle upwards. Where oceanic crust meets meets less dense continental crust, the oceanic crust id forced under the continental crust. The continental crust is buckled by the impact. This is how folded mountain ranges, such as the Appalachian mountains in North America, were formed. Fold mountains are also formed where two areas of continental crust meet. The Himalayas, for example, began to form when India collided with Asia, buckling the sediments and parts of the oceanic crust between them. block mountains are formed when a block of land is up lifted between two faults as a result of compression or tension in the Earth's crust. Often, the movement along faults has taken place gradually over millions of years. How ever, two plates may cause an earthquake by suddenly sliding past each other along a fault line.