Apa Sebabnya Di Pegunungan Udara Malah Dingin

Ketika kita mencoba memecahkan pertanyaan mengapa di pegunungan justru udara lebih dingin padahal lebih dekat posisinya dengan matahari, kita akan berfikir seharusnya lebih panas. Itu mungkin yang terlintas sekilas dipikiran kita jika kita tidak mau cari tahu tentang penjelasan ilmiahnya.

Selengkapnya >>

Mengenal Satuan Panjang, Berat, Isi dan Luas

Kita sering mendengar beberapa satuan yang menurut kita mungkin tidak sering digunakan di negara kita, seperti pond, kaki, barrel. Berikut adalah satuan-satuan dengan konversinya, yang bisa membantu anda untuk memahaminya.

Selengkapnya >>

Mengenal Simbol - simbol Dalam Ilmu Fisika

Sangatlah perlu mengetahui simbol-simbol dan artinya jika sedang mempelajari ilmu fisika karena hal itu sering digunakan. Sehingga  kita tidak sampai sering lupa atau bertanya-tanya sedangkan kita adalah seorang pelajar. Berikut simbol-simbol yang dipakai dalam ilmu fisika yang berlaku secara internasional.

Selengkapnya >>

ARUS DAN TEGANGAN

Arus listrik adalah banyaknya muatan listrik yang mengalir tiap satuan waktu. Muatan listrik bisa mengalir melalui kabel atau penghantar listrik lainnya.
I = Q/T
Pada zaman dulu, Arus konvensional didefinisikan sebagai aliran muatan positif, sekalipun kita sekarang tahu bahwa arus listrik itu dihasilkan dari aliran elektron yang bermuatan negatif ke arah yang sebaliknya.Satuan SI untuk arus listrik adalah ampere (A).

Tegangan listrik (kadang disebut sebagai Voltase) adalah perbedaan potensi listrik antara dua titik dalam rangkaian listrik, dinyatakan dalam satuan volt. Besaran ini mengukur energi potensial sebuah medan listrik untuk menyebabkan aliran listrik dalam sebuah konduktor listrik. Tergantung pada perbedaan potensi listrik satu tegangan listrik dapat dikatakan sebagai ekstra rendah, rendah, tinggi atau ekstra tinggi.
V= I .R
Satuan SI untuk Tegangan adalah volt (V).

Selengkapnya >>

GERAK LURUS BERUBAH BERATURAN (GLBB)

Gerak lurus adalah gerak pada suatu benda melalui lintasan garis lurus. Contohnya seperti gerak rotasi bumi, gerak jatuh buah apel, dan lain sebagainya. Gerak lurus dapat kita bagi lagi menjadi beberapa jenis, yaitu :
a. Gerak lurus beraturan (GLB)
Gerak lurus beraturan adalah gerak suatu benda yang lurus beraturan dengan kecepatan yang tetap dan stabil.
Misal :
- Kereta melaju dengan kecepatan yang sama di jalur rel yang lurus
- Mobil di jalan tol dengan kecepatan tetap stabil di dalam perjalanannya.
b. Gerak lurus berubah beraturan (GLBB)
Gerak lurus berubah beraturan adalah gerak suatu benda yang tidak beraturan dengan kecepatan yang berubah-ubah dari waktu ke waktu.
Misalnya :
- Gerak jatuhnya tetesan air hujan dari atap ke lantai
- Mobil yang bergerak di jalan lurus mulai dari berhenti sumber : e-dukasi.net

Selengkapnya >>

ELECTRICITY A GREAT AID TO MODERN LIVING

Can you imagine modern living without electricity? No Aeroplanes would be able to take off, no car engines would run, radio and television broadcast would stop. In other words, modern living could not go on. Besides, millions of people mechanics factory, pilots etc would lose their jobs, for they can work only if electricity is available. Electricity is undoubtedly one of the most important aids to modern living.

Electricity is produces by a generator containing a coil of wire and magnet. The magnet is either straight or in the form a horse shoe. By moving the coil around outside of straight magnet electricity is generated.Another way is to turn the coil around inside of a horse shoe magnet. Or the coil can be held still and electricity is produces by moving the magnet backwards and forwards inside the coil. The electricity that we use in our daily life is generated in a power station. There you will find one or more big generators, which as operated by engine, steam, or water power. A large water wheel is found inside a power station which is run by a waterfall. This wheel is turned by the falling water, which pushes hard against its teeth. It turns round and round. A large shaft joins the wheel to a coil of wire. As the wheel turns, the coil turns too thus producing electricity.

On the same principles, steam power can be used to turn a turbine, which works like the water wheel. A shaft that joins the turbine to a coil of wire makes the coil turn as the turbine turns. Thus, electricity is produced. In a simple way, a coil can also be turned round by the power from a diesel engine. That is another way to produce electricity.

Electricity can produce light and heat, and perform various kinds of mechanical work such as lifting, turning, pulling, pushing and swinging. Electric current travels to our homes through wires in a complete circuit, and this is why there must be two pieces of wire connected to a bulb. In the bulb there is a fine wire that has high resistance against electric current. When the electric current passes through it, the energy used in overcoming the resistance will produce heat. When this fine wire becomes so hot that it shines, light is produced. A neon lamp usually in the form of a tube, however, produces light in a different way. Te tube is filled with neon gas. When the electric current passes through the gas, ultraviolet rays are formed. As the ultraviolet rays strike the inside of the tube, which is coated with a certain mineral, light is produced. The neon lamp produces more light for the same amount of electricity being used than the ordinary electric lamp. Moreover, its light is cool. In an electric stove or iron the electricity works almost in the same way as that in the ordinary electric lamp. 

The only difference is that in the two former utensils the wire has a higher resistance that enables it to produce more heat. This can be made by applying a wire of a different size and resistance.

Various kinds of mechanical work like those we have mentioned above can be performed by applying a dynamo to change the electricity into mechanic power, which is widely used in large factories, harbours, as well as in bridge and building construction.

Each electrical appliance uses a certain amount of electricity. When too many appliance are connects in the same circuit, the wire has to carry too heavy a load of electricity. A too heavily loaded wire will heat up and cause a fire, and this can be dangerous. Accordingly, a fuse is needed to break the circuit to stop the electric current. Inside the fuse there is a fine wire, which blows when too much electricity passes through it. The fuse is places as a part of the wire going to the house. This means that all electric current going to the house must pass through it. In short, the current will break automatically when the fuse blows. A short circuit occurs when two uncovered wires in the house touch each other so that the current flows directly from one wire to the other, causing too much current. To avoid this, all wires in the house must be covered or insulated with rubber or plastic.

Electricity is indeed a great aid to modern living, but at times it can be very dangerous, especially when you do not know how it work. So be careful.

Selengkapnya >>

GRAVITY

A force of attraction exist between every body in the universe. It is called gravity and it has been investigated by many scientists including Galileo and Newton. This gravitational force depends on the masses of the bodies involved. Normally it is very small, but when one of the bodies is a planet, like the earth, the force is considerable. Everything on or near the surface of the earth is attracted by the mass of the earth. The greater the mass, the greater is the earth’s forces of attraction on it.

We call this force of attraction gravity.

Because of the gravity, bodies have weight. We can perceive weight only when a body resists gravity. For example, when we pick up a stone there are two forces involved. One is the lifting force we exert, and the other is the force of gravity which attracts the stone downwards and thus gives it weight. When a body escapes from the influence of the earth’s gravitational pull, it can become weightless. For example, the centrifugal force of a spacecraft spinning in orbit round the earth cancles the effect of gravity. The crew therefore experience weightlessness. One of the minor disadvantages of weightlessness is that normal pens will not write, because the ink is not attracted by gravity to flow out of the pen.

If the space crew land on the surface of the moon, they experience the much weaker force of gravity exerted by the moon. On the moon they weigh less than on the earth. Special training is necessary to help them to walk on the moon’s surface.

To simplify engineering calculations, it is assumed that gravity is the same everywhere on the earth’s surface, and that for every kilogram of mass the earth exerts a force of 9.81 Newton on a body. In fact gravity differs slightly from place to place because of the shape of the earth. It is greatest at the poles where the earth is flattest and is the least at the equator. (adapted from English in mechanical engineering by Eric H. Glendinning)

Selengkapnya >>

TURBINES

The main difference between the turbine and other types of engine is that its only movement is rotary, or turning. Its name comes from Latin turbo, meaning something that spins or twirls.

Turbines can be driven by steam water, gas or air. A steam turbine consists of a cylinder shaped casing containing a drum shaped rotor, or turning part. Steam from the boiler is led through nozzles fixed to the casing so that jets of steam strike blades are mounted in a ring round the rotor.

Water turbines are used for driving generators in hydroelectric power station. There are two types, impulse turbines and reaction turbines. Both make use of the energy of falling water which increases in velocity as it falls under the influence of gravity. The distance of fall or head, corresponds to steam pressure. A high head or steam pressure results in high water or steam velocity.

Gas turbines work on the same principle as steam or water turbines, but are driven by hot gas which is produced by burning liquid fuel such as paraffin, heavier oils, or gas in air. The gas is compressed by a rotary compressor, heated by burning the fuel, and blown into the gas turbine. Developed originally to drive aircraft, their outputs and sizes have been increased tremendously. They are now used widely for ship propulsion and in power stations.

Tiny air turbines, driven by compressed air and turning at 250.000 r.p.m are used for dentists drills. At this speed the drilling of a tooth is quickly completed and there is less vibration than with an electric drill.

Selengkapnya >>

Tim Olimpiade Fisika Indonesia (TOFI)

Kompetisi Soal

Jumat, 7 Jan 2011 07:54

Kompetisi pembuatan soal untuk tahap final WoPho (World Physics Olympiad). Peraturan dasar:

Fase Seleksi World Physics Olympiad

Jumat, 7 Jan 2011 07:41

Fase seleksi WoPhO (World Physics Olympiad) telah dimulai. WoPho adalah kompetisi fisika tingkat SMA. Pada fase seleksi terdapat 10 soal teori yang menarik yang dapat didownload di http://www.wopho.org/selection.php. Batas akhir pengumpulan solusinya adalah 30 Juni 2011. Seratus peserta terbaik berhak untuk berpartisipasi pada babak final di Bali, 28 Desember 2011- 3 Januari 2012.

World Physics Olympiad

Jumat, 7 Jan 2011 07:01

World Physics Olympiad adalah suatu lomba fisika individu tingkat SMA yang diinisiasi oleh Prof. Yohanes Surya Ph.D. (Pendiri Tim Olimpiade Fisika Indonesia, Surya Institute dan Sekolah Tinggi Keguruan Ilmu Pendidikan Surya).

Indonesia sabet 4 emas dalam olimpiade Fisika Internasional di Zagreb, Kroasia

Sabtu, 24 Jul 2010 20:27

Siswa-siswa Indonesia kembali mengharumkan nama bangsa di kancah internasional. Lima siswa Indonesia meraih 4 medali emas dan 1 medali perak dalam Olimpiade Fisika Internasional ke 41 yang diadakan di Zagreb, Kroasia.

Hasil akhir Tim Indonesia di IPhO 40 Merida Mexico

Sabtu, 18 Jul 2009 08:10

Akhirnya tim Indonesia harus puas dengan 1 medali emas, 3 perak dan 1 perunggu di event IPhO 40 Merida Mexico. Prestasi ini patut dibanggakan meskipun meleset dari target yang ditetapkan pada saat pelepasan tim yaitu 2 medali emas. 

TOFI berhasil memenuhi target dengan meraih 2 Emas, 4 Perak dan 2 Perunggu

Senin, 4 Mei 2009 15:17

Sesuai dengan prediksi awal sebelum keberangkatan tim, Hendra Kwee, Ph.D. menargetkan perolehan medali minimal 2 medali emas. Ternyata target tersebut terpenuhi dengan merebut 2 Emas, 4 Perak dan 2 Perunggu, bahkan tanpa diduga sebelumnya salah satu anggota tim juga merebut predikat "The best experiment". Dengan demikian seluruh anggota tim APhO X Bangkok, 24 April - 2 Mei 2009 berhasil membawa pulang medali. Terlihat dalam foto dari kiri : Dzuhri Radityo Utomo SMAN 1 Yogyakarta, DIY (Emas); Fernaldo Richtia Winnerdy SMAK BPK Penabur Gading Serpong, Banten (Perak); Muhammad Sohibul Maromi SMAN 1 Pamekasan, Jawa Timur (Perunggu); Paul Zakharia Fajar Hanakata SMAN 1 Denpasar, Bali (Perak); Winson Tanputraman SMAK 1 BPK Penabur, DKI Jakarta (Emas dan "The best experiment"); Sandoko Kosen SMA Sutomo 1 Medan, Sumatera Utara (Perak); Brigitta Septriani SMA Santu Petrus Pontianak, Kalimantan Barat (Perunggu); dan Andri Pradana SMAK 1 BPK Penabur, DKI Jakarta (perak). Prestasi tahun ini lebih baik dari tahun-tahun sebelumnya karena ini adalah pertama kalinya seluruh anggota tim Indonesia meraih minimal medali perunggu.

Tim Indonesia berhasil meraih 2 medali emas di IPhO ke-39 di Vietnam

Senin, 28 Jul 2008 10:55

Tim Olimpiade Fisika Indonesia (TOFI) yang membawa lima siswa ke ajang Olimpiade Fisika Internasional (International Physics Olympiad/IPhO) ke-39 di Hanoi, Vietnam berhasil meraih 2 medali emas, 2 medali perak dan 1 medali perunggu. Kegiatan yang telah dilaksanakan tanggal 20 Juli – 29 Juli 2008 ini diikuti oleh 82 negara dengan jumlah peserta mencapai 376 siswa. http://www.tofi.or.id/

Selengkapnya >>