The Internet: is it always safe?21.05.2011At present we cannot imagine our life without the Internet. The Internet is necessary for each person. It is an integral part of our life. All people use the Internet on different purposes: for dialogue, for searching the information, for work, for studying, for fun and entertainment. We search something with the help of the searching engine. I think that the most important problem of the Internet is the addiction of people to it. Some people surf the Internet for many days and forget about their relatives and real life.Nevertheless the Internet has many pluses. By means of the Internet it is possible to meet new friends, to communicate with them. You can find any information, learn main news.Meanwhile the Internet has minuses. These are viruses. And as I have alreadyMentioned, it`s The Internet addiction, which breaks people`s life. Also sometimes the speed of the Internet is very low, so it`s impossible to use it in an effective way.As for me, the Internet is a dialogue, searching for various information. The Internet is very important and also it is a necessary thing.The Internet is not safe. But you can use different programs for safe using of the Internet. With the Internet it is easier to live.For example it can be a good source of information for school and for personal interests. Also it gives us dialogue with different people from different cities, but doing this you can sit in a convenient armchair. You can shop with the help of the Internet. It is possible to exchange and download any files in the Net. And at last it is possible to play computer games with other players.But there are some dangers. In the Internet people can break your computer in and make many bad tricks that will lead to bad mood. You can be deceived for some sum of money.The Internet is not safe but if you use an excellent antivirus program you willNot have any problems.It is impossible to live now without the Internet. Different professionals are connected with the Internet. And in the end, the Internet facilitates our life and makes it easier and comfortable. The whole world uses the Internet! Join it!A lot of people can`t imagine their life without the Internet. There is the Internet at school, in the houses, in some clubs and even in the mobile phones. But is the Internet safe?On the one hand, there are a lot of pluses. First of all, there are many antivirus programs nowadays, so we can be sure that there are no viruses on our PC. Then, a lot of sites that have registration have an option to change password, so robots can`t send spam from their address. Finally, when children enter 18+ sites by chance, there is a special message beforehand, so the information can`t traumatize their minds.But on the other hand, there are some minuses too. For example, a lot of antivirus programs can`t stop the viruses at the right time and detect them. All passwords can be hacked. SoTry to change them sometimes. Speaking about messages, some children don`t pay attention to them or open them because of curiosity.So, as you see, the Internet can be good and bad at the same time, so you should chose what the Internet is for you.Many people think that the Internet is a part of their life. But does it have only good things – that is the topic we are going to discuss.One of the main advantages of the Internet is much different information. You can download many interesting films, sounds, books, computer games, programs for your computer. Furthermore you can read news about subject which is interesting for you. Also you can chat and send mails to your friends.On the other hand, there are many disadvantages about using the Internet. Firstly, you can get viruses on your computer by visiting any web-sites you don`t trust and downloading files from them. Also you can get blackmail or spam. Using the Internet for many hours is not good for your sight.The Internet is neither good nor bad, it can beDangerous and useful at the same time, and everyone should make his own choice to use it or not.
Пока оно висит, на него действует сила тяжести: Fт=m*g. Зная объём тела (переводим в кубометры - 2,5*10^(-3)) и плотность (для меди - 8,92*10^3 кг/м^3), найдём массу: m=V*p=2,5*10^(-3)*8,92*10^3 = 22,3 кг И отсюда сила тяжести: Fт=22,3*10 = 223 Н Именно столько будет показывать динамометр в воздухе. Но при погружении в жидкость на погруженную часть начнёт действовать сила Архимеда, равная Fа=p*g*V (тут надо не путать, плотность не тела, а жидкости, а объём только погружённой части!) Погружённый объём, по условию, равен половине общего: V=1/2*2,5*10^(-3)=1,25*10^(-3) м^3 Плотность воды p=1000 кг/м^3 Отсюда: Fa=1000*10*1,25*10^(-3)=12,5 Н В итоге на динамометре отразится равнодействующая сила. Так как исходные силы противонаправлены (тяжести - вниз, Архимеда - вверх), то она будет равна их разности: R=Fт-Fа=223-12,5=210,5 Н
m=V*p=2,5*10^(-3)*8,92*10^3 = 22,3 кг
И отсюда сила тяжести:
Fт=22,3*10 = 223 Н
Именно столько будет показывать динамометр в воздухе. Но при погружении в жидкость на погруженную часть начнёт действовать сила Архимеда, равная Fа=p*g*V (тут надо не путать, плотность не тела, а жидкости, а объём только погружённой части!)
Погружённый объём, по условию, равен половине общего: V=1/2*2,5*10^(-3)=1,25*10^(-3) м^3
Плотность воды p=1000 кг/м^3
Отсюда: Fa=1000*10*1,25*10^(-3)=12,5 Н
В итоге на динамометре отразится равнодействующая сила. Так как исходные силы противонаправлены (тяжести - вниз, Архимеда - вверх), то она будет равна их разности: R=Fт-Fа=223-12,5=210,5 Н