Thursday, February 28, 2013

HOAX, Jatuhnya UFO Menyebabkan Jutaan Ikan Mati di Jepang

28 comments
Pada akhir tahun 2012 hingga bulan Januari 2013 yang lalu, heboh berita tentang jatuhnya UFO di Jepang. Akibat dari jatuhnya UFO tersebut dikabarkan menyebabkan jutaan ikan mati di sana, di tepatnya di kota Okinawa.
Berikut gambar yang terpasang di beberapa situs yang menginformasikan berita ini :


Berita ini di informasikan, diantaranya di situs Veterans TodayIn Other Newz dan Inilah.com.
Namun, benarkah berita ini?
Jika benar, mengapa tidak ada informasi dari saksi, atau gambar mengenai UFO yang dituding menjadi penyebab jutaan ikan mati mendadak di sana? Dan jika berita ini benar, tentu ini adalah sesuatu yang dapat membuat para pengamat UFO di seluruh dunia sedikit merasa "gembira" karena Objek yang selama ini mereka pelajari dan dianggap samar oleh kebanyakan orang adalah nyata.

Namun sayang, saat dicari  tahu lebih lanjut mengenai informasi ini ternyata cukup mengecewakan. Karena usut punya usut, ternyata berita tentang jatuhnya UFO di Okinawa ini adalah hoax alias bohong...

Tidak penah diketahui ada UFO yang jatuh di kota Okinawa, Jepang hingga menyebabkan jutaan ikan mati disana. Adapun gambar nelayan yang berada di tengah ikan-ikan mati itu adalah gambar ikan-ikan mati yang terkontaminasi air limbah di provinsi Hubei, China pada tahun 2007 (www.sme.sk). Bukan di Okinawa, Jepang tahun 2012.

hmm... terbukti deh, berita tentang Jatuhnya UFO yang menyebabkan jutaan ikan mati mendadak di Okinawa, adalah hoax.

Wednesday, February 27, 2013

Tes IQ yuuk...

36 comments
Assalamualaikum...

Test IQ (Inteligent Quotient) adalah test yang nilainya mencerminkan kecerdasan Individu yang menjalani test tersebut, test IQ ada bermacam-macam jenisnya, ada yang berbentuk pertanyaan tulis, ada pula yang berbentuk pertanyaan dalam gambar.

Kata "kecerdasan", yang tertulis diatas merupakan istilah umum yang digunakan untuk menjelaskan sifat pikiran yang mencakup sejumlah kemampuan, seperti kemampuan menalar, merencanakan, memecahkan masalah, berpikir abstrak, memahami gagasan, menggunakan bahasa, dan belajar.

Kecerdasan erat kaitannya dengan kemampuan kognitif yang dimiliki oleh individu. Kecerdasan dapat diukur dengan menggunakan alat psikometri yang biasa disebut sebagai tes IQ. Ada juga pendapat yang menyatakan bahwa IQ merupakan usia mental yang dimiliki manusia berdasarkan perbandingan usia kronologis.

Adapun fungsi dari tes IQ adalah :
1. Dapat mengetahui kecerdasan yang dimiliki

2. Dapat melihat sejauh mana potensi bisa dikembangkan secara maksimal

3. Untuk mengkreasikan antara tingkat kecerdasan dengan hasil belajar yang dicapai (jika IQ tinggi harusnya prestasi belajar juga tinggi)

4. Untuk mendeteksi kesulitan belajar disebabkan karena faktor kemampuan ataukah faktor yang lain seperti kemalasan, dan lain-lain

5. Untuk pertimbangan dalam memilih jenjang pendek/panjang

Ketika masih duduk di bangku SMP dan SMA dulu, aku dan mungkin juga kamu... pernah mengikuti beberapa kali tes IQ. Kalau menurut aku, tes semacam ini menyenangkan. Apalagi hasil skornya yang selalu membuat penasaran, ya kan? heheh... Beberapa waktu yang lalu, saya mengikuti tes IQ online di internet. Skornya bisa langgsung diketahui, tanpa harus menunggu lama.

Nah, pada kesempatan kali ini... aku mau berbagi link situs yang menyediakan tes IQ secara online, yang mungkin akan bermanfaat buat kamu, yaitu :
3. IQ Elite

Ketiga tes IQ di situs tersebut udah pernah aku ikutin, dan gratis lho...
Ini hasil tes IQ aku, masing-masing dari Quick IQ Test, Tes IQ Online dan IQ Elite :







Penasaran pengen tahu berapa skor IQ kamu?, langsung aja ikutin tes nya... Gak harus semua kok, salah satu link nya saja.

Perlu diketahui
Menurut Howard Gardner, psikolog pendidikan asal Amerika yang terkenal dengan teori kecerdasan gandanya menyatakan, kecerdasan intelektual hanyalah salah satu dari 8 kecerdasan yang dimiliki seseorang. Kecerdasan ganda yang dimaksud Gardner adalah kecerdasan di bidang bahasa, berpikir logis atau matematis, musik, visual (penglihatan) dan gerak.

Jadi, tes IQ seperti ini sekedar untuk memberi gambaran/potret diri kita yang selanjutnya akan/harus kita tindak lanjuti dengan cara yang tepat. Jika kemampuan rendah tentu tidak cukup belajar hanya sambil lalu saja. Demikian pula jika tes hasil tinggi juga tidak memberikan manfaat jika tidak diasah secara maksimal. Tes yang kita lakukan mungkin hasilnya tidak mutlak benar 100%. Ada angka-angka kemungkinan kesalahan prediksi walaupun itu kecil. Jika kita mendapatkan skor yang rendah tidak perlu minder atau berkecil hati karena keberhasilan seseorang tidak mutlak ditentukan oleh tingginya angka kecerdasan kita tapi juga banyak dipengaruhi oleh faktor yang lain seperti usaha, kerja keras, ketabahan, keuletan, ketelatenan dan do’a.

Oh iya, silahkan baca juga tulisan saya yang berjudul "IQ Tak Tinggi Tapi Menarik"

Semoga bermanfaat yaa,
Wassalamualaikum... Wr, Wb.

Reaksi Fisi dan Reaksi Fusi

2 comments
Assalamualaikum....

Reaksi inti, seperti halnya reaksi elektronik, melibatkan perubahan energi. Akan tetapi, perubahan energi dalam reaksi inti bersifat sertamerta dan berantai sehingga perlu pengetahuan dan teknologi tinggi untuk mengembangkan reaktornya.Ada tiga jenis reaktor nuklir, yaitu reaktor untuk reaksi fusi, reaktor fisi, dan reaktor pembiak.


1. Reaksi Fisi
Reaksi fisi adalah reaksi pembelahan nuklida radioaktif menjadi nuklida-nuklida dengan nomor atom mendekati stabil. Pembelahan nuklida ini disertai pelepasan sejumlah energi dan sejumlah neutron. Reaksi fisi inti uranium–235 dioperasikan dalam reaktor tenaga nuklir untuk pembangkit tenaga listrik. Jika inti 235U dibombardir dengan neutron, akan dihasilkan inti-inti atom yang lebih ringan, disertai pelepasan energi, juga pelepasan neutron sebanyak 2 hingga 3 buah. Jika neutron dari setiap reaksi fisi bereaksi lagi dengan inti 235U yang lain, inti-inti ini akan terurai dan melepaskan lebih banyak neutron. Oleh karena itu, terjadi reaksi yang disebut reaksi berantai (chain reaction).

Reaksi fisi 235U dengan neutron
Reaksi fisi 235U dengan neutron membentuk kripton dan barium
disertai
pelepasan energi sebesar 3,5 × 10-11 J
dan sejumlah neutron yang siap bereaksi fisi dengan inti yang lain.

Reaksi berantai adalah sederetan reaksi fisi yang berlangsung spontan dan serta merta, disebabkan oleh neutron yang dilepaskan dari reaksi fisi sebelumnya bereaksi lagi dengan inti-inti yang lain. Oleh karena satu reaksi fisi dapat menghasilkan 3 neutron, jumlah inti yang melakukan fisi berlipat secara cepat, seperti ditunjukkan pada Gambar 5.17. Reaksi berantai dari fisi inti merupakan dasar dari reaktor nuklir dan senjata nuklir.

Reaksi berantai pada reaksi fisi
Reaksi berantai pada reaksi fisi
Agar dapat memanfaatkan reaksi berantai dari suatu sampel radioaktif yang berpotensi fisi maka reaksi fisi harus dikendalikan dengan cara mengendalikan neutron yang dilepaskan dari reaksi itu. Dengan demikian, hanya satu neutron yang dapat melangsungkan reaksi fisi berikutnya. Berdasarkan hasil pengamatan, jika sampel radioaktif terlalu sedikit, neutron-neutron yang dihasilkan dari reaksi fisi meninggalkan sampel radioaktif sebelum neutron-neutron itu memiliki kesempatan untuk bereaksi dengan inti-inti radioaktif yang lain. Dengan kata lain, terdapat massa kritis untuk bahan tertentu yang berpotensi fisi, yang dapat melangsungkan reaksi berantai (lihat Gambar dibawah ini). 
Massa kritis adalah massa terkecil dari suatu sampel yang dapat melakukan reaksi berantai.

Konstruksi bom atom
Kontruksi Bom atom
Jika massa terlalu besar (super kritis), jumlah inti yang pecah berlipat secara cepat sehingga dapat menimbulkan ledakan dan petaka bagi manusia, seperti pada bom atom. Bom atom merupakan kumpulan massa subkritis yang dapat melakukan reaksi berantai. Ketika dijatuhkan massa subkritis menyatu membentuk massa super kritis sehingga terjadi ledakan yang sangat dahsyat.

Ledakan bom menyerupai cendawan
Ledakan bom yang menyerupai cendawan
Reaktor fisi nuklir adalah suatu tempat untuk melangsungkan reaksi berantai dari reaksi fisi yang terkendali. Energi yang dihasilkan dari reaktor ini dapat dimanfaatkan sebagai sumber energi nuklir. Reaktor nuklir terdiri atas pipa-pipa berisi bahan bakar radioaktif dan batang pengendali neutron yang disisipkan ke dalam pipa bahan bakar nuklir tersebut. Perhatikan Gambar :

Skema bagian inti dari reaktor nuklir
Skema bagian inti dari reaktor nuklir
Pipa bahan bakar berbentuk silinder mengandung bahan yang berpotensi fisi. Dalam reaktor air ringan (1H2O), pipa bahan bakar berisi uranium yang berpotensi melangsungkan reaksi fisi. Uranium yang digunakan sebagai bahan bakar dalam reaktor nuklir mengandung isotop 235U sekitar 3%. Batang pengendali neutron dibuat dari bahan yang dapat menyerap neutron, seperti boron dan kadmium sehingga dapat mengendalikan reaksi berantai. Pengendalian neutron dilakukan dengan cara menaikkan atau menurunkan batang pengendali yang disisipkan dalam pipa bahan bakar.

Dalam keadaan darurat, batang-batang pengendali ini, dapat dimasukkan seluruhnya ke dalam pipa bahan bakar guna menghentikan reaksi fisi. Selain batang pengendali, terdapat alat yang disebut moderator Moderator ini berguna untuk memperlambat gerakan neutron. Moderator dipasang jika bahan bakar uranium–235 merupakan fraksi terbanyak dari total bahan bakar. Moderator yang dipakai umumnya air berat (2H2O), air ringan (1H2O), atau grafit.

Bahan bakar nuklir, selain uranium–235, juga uranium–238 dapat dijadikan bahan bakar. Keunggulan dan kelemahan dari kedua bahan bakar tersebut, yaitu jika uranium–238, bereaksi lebih cepat dengan neutron hasil reaksi fisi dibandingkan uranium–235, tetapi uranium–235 bereaksi lebih cepat dengan neutron yang telah diperlambat oleh moderator.
Pada reaktor air ringan, 1H2O berperan sebagai moderator, sekaligus sebagai pendingin. Gambar berikut menunjukkan rancang bangun reaktor air bertekanan atau reaktor air ringan.
Reaktor nuklir air ringan
Reaktor nuklir air ringan (konstruksi air bertekanan) Batang bahan bakar memanaskan air yang disirkulasikan ke penukar kalor. Uap yang dihasilkan dalam penukar kalor dilewatkan ke turbin yang mendorong generator listrik.
Air dalam reaktor dipertahankan sekitar 350°C pada tekanan 150 atm agar tidak terjadi pendidihan. Air panas ini disirkulasikan menuju penukar kalor, di mana kalor digunakan untuk menghasilkan uap, dan uap tersebut menuju turbin untuk pembangkit listrik. Setelah periode waktu tertentu, hasil reaksi fisi yang menyerap neutron berakumulasi dalam pipa bahan bakar. Hal ini menimbulkan interferensi dengan reaksi rantai sehingga pipa bahan bakar harus diganti secara berkala.

Buangan sisa bahan bakar menjadi limbah nuklir. Limbah ini dapat diproses ulang. Bahan bakar sisa tersebut dipisahkan secara kimia dari limbah radioaktif. Plutonium–239 adalah salah satu jenis bahan bakar hasil pemisahan dari buangan limbah nuklir. Isotop ini diproduksi selama reaktor beroperasi, yaitu pemboman uranium–238 oleh neutron. Isotop plutonium–239 juga berpotensi fisi dan dipakai untuk membuat bom atom atau senjata nuklir. Ketersediaan isotop plutonium–239 dalam jumlah besar akan meningkatkan kesempatan negara-negara maju untuk menyalahgunakan plutonium dijadikan bom atom atau senjata nuklir pemusnah masal. Sisa bahan bakar nuklir sebaiknya tidak didaur-ulang. Masalah utama bagi lembaga tenaga nuklir adalah bagaimana membuang sampah radioaktif yang aman.

2. Reaksi Fusi
Reaksi fusi adalah reaksi nuklida-nuklida ringan digabungkan menjadi nuklida dengan nomor atom lebih besar. Misalnya, inti deuterium (2H) dipercepat menuju target yang mengandung deuteron (2H) atau tritium (3H) membentuk nuklida helium. 
Persamaannya:
1H2 + 1H22He3 + 0n1
1H2 + 1H32He4 + 0n1

Untuk mendapatkan reaksi fusi inti, partikel pembom (proyektil) harus memiliki energi kinetik yang memadai untuk melawan tolakan muatan listrik dari inti sasaran (lihat Gambar dibawah ini).
Grafik energi antaraksi dua inti terhadap tolakan elektrostatis
Grafik energi antaraksi dua inti terhadap tolakan elektrostatis
Disamping pemercepat partikel, cara lain untuk memberikan energi kinetik memadai kepada inti proyektil agar dapat bereaksi dengan inti sasaran dilakukan melalui pemanasan inti sasaran hingga suhu sangat tinggi. Suhu pemanasan inti sasaran sekitar 108 °C. Pada suhu ini semua elektron dalam atom mengelupas membentuk plasma.

Plasma adalah gas netral yang mengandung ion dan elektron. Masalah utama dalam mengembangkan reaksi fusi terkendali adalah bagaimana kalor plasma yang bersuhu sangat tinggi dapat dikendalikan. Kendalanya, jika plasma menyentuh bahan apa saja, kalor dengan cepat dihantarkan dan suhu plasma dengan cepat turun. Reaktor uji fusi inti Tokamak menggunakan medan magnet berbentuk donat untuk mempertahankan suhu plasma dari setiap bahan, seperti ditunjukkan pada Gambar dibawah ini.

Reaksi fusi inti tokamak
Reaksi fusi inti tokamak

Sekian... semoga bermanfaat,
Wassalamualaikum... Wr, Wb.



sumber dan referensi :
Budisma.web
Shvoong.com

Versatile Blogger Award

42 comments
Assalamualaikum...


Alhamdulillah... senaaaaaannng sekali.
Setelah  minggu lalu dapat dua Company Award dari bang Albar dan Pak Dede, sekarang bang Albar yang cute dan baik hati kembali memberikan award buat aku. Dan kali ini nama awardnya adalah :
Versatile Blogger Award


Versatile Blogger Award ini  adalah award ke-10 buat saya. Yippie... udah punya sepuluh award nih, hihihi.... Alhamdulillah...
Nah, karena aku lagi happy dan sekaligus juga menyampaikan amanat dari pemberi awardnya, saya akan berbagi dengan sahabat-sahabat Blogger saya.

Oh iya... award ini ada syaratnya lho,
1. Nominate 15 fellow bloggers.
2. Let the nominated bloggers know that they have been nominated for this award.
3. Share 7 random facts about yourself.
4. Thank the blogger who has nominated you.
5. Add the Versatile Blogger Award to your post.

Oke... yang pertama, saya akan berbagi award ini dengan 15 Blogger sahabat saya, yaitu:
1. Mas Hanif
2. Reo Adam
3. Artabez
4. Budi os 19
5. Agung Talaga
6. Mas Yusa
7. Andy Borneo
8. Tia Blog
9. Fadly
10. Belajar Photoshop
11. Rohis Facebook
12. Agung Gusrianto
13. Mohamad Rivai
14. Eka Ikhsanudin
15. Fika Thiana

Tujuh fakta tentang saya adalah... tidak suka telur, berponi, gak bisa tidur kalau gak pakai kaos kaki, rendang lover, suka tentang UFO/Alien, sering lupa waktu kalau internetan dan pengen banget memelihara singa., hehehe...

Itulah tujuh fakta tentang saya dan nama-nama sahabat blogger yang mendapat Versatile Award Blogger dari saya... semoga kalian senang menerimanya, selamat ya...
Dan buat bang Albar, sekali lagi terimakasih banyak yaa udah memberikan award ini buat aku, terimakasih...

Wassalamualaikum... Wr, Wb.

Our Solar System: Moons

No comments
Assalamualaikum...

This photo illustration shows selected moons of
our solar system at their correct relative
sizes to each other and to Earth.
Moons -- also called satellites -- come in many shapes, sizes and types. 
They are generally solid bodies, and few have atmospheres. Most of the planetary moons probably formed from the discs of gas and dust circulating around planets in the early solar system.

Astronomers have found at least 146 moons orbiting planets in our solar system. This number does not include the six moons of the dwarf planets, nor does this tally include the tiny satellites that orbit some asteroids and other celestial objects. Another 25 moons are awaiting official confirmation of their discovery.

Of the terrestrial (rocky) planets of the inner solar system, neither Mercury nor Venus have any moons at all, Earth has one and Mars has its two small moons. In the outer solar system, the gas giants Jupiter and Saturn and the ice giants Uranus and Neptune have numerous moons. As these planets grew in the early solar system, they were able to capture objects with their large gravitational fields.

Earth's Moon probably formed when a large body about the size of Mars collided with Earth, ejecting a lot of material from our planet into orbit. Debris from the early Earth and the impacting body accumulated to form the Moon approximately 4.5 billion years ago (the age of the oldest collected lunar rocks). Twelve American astronauts landed on the Moon during NASA's Apollo program from 1969 to 1972, studying the Moon and bringing back rock samples.

Usually the term moon brings to mind a spherical object, like Earth's Moon. The two moons of Mars, Phobos and Deimos, are different. While both have nearly circular orbits and travel close to the plane of the planet's equator, they are lumpy and dark. Phobos is slowly drawing closer to Mars and could crash into the planet in 40 or 50 million years. Or the planet's gravity might break Phobos apart, creating a thin ring around Mars.

Jupiter has 50 known moons (plus 16 awaiting official confirmation), including the largest moon in the solar system, Ganymede. Many of Jupiter's outer moons have highly elliptical orbits and orbit backwards (opposite to the spin of the planet). Saturn, Uranus and Neptune also have some irregular moons, which orbit far from their respective planets.

Pan is responsible for a gap in Saturn's rings.
Saturn has 53 known moons (plus 9 awaiting official confirmation). The chunks of ice and rock in Saturn's rings (and the particles in the rings of the other outer planets) are not considered moons, yet embedded in Saturn's rings are distinct moons or moonlets. These shepherd moons help keep the rings in line. Saturn's moon Titan, the second largest in the solar system, is the only moon with a thick atmosphere.

In the realm of the ice giants, Uranus has 27 known moons. The inner moons appear to be about half water ice and half rock. Miranda is the most unusual; its chopped-up appearance shows the scars of impacts of large rocky bodies.

Neptune has 13 known moons. And Neptune's moon Triton is as big as the dwarf planet Pluto and orbits backwards compared with Neptune's direction of rotation.
Pluto's large moon Charon is about half the size of Pluto. Like Earth's Moon, Charon may have formed from debris resulting from an early collision of an impactor with Pluto. In 2005, scientists using the Hubble Space Telescope to study Pluto found two additional, but very small, moons. The little moons Nix and Hydra are about two to three times as far from Pluto as Charon and roughly 5,000 times fainter than Pluto. Eris, another dwarf planet even more distant than Pluto, has a small moon of its own, named Dysnomia. Haumea, another dwarf planet, has two satellites, Hi'iaka and Namaka.

How the Moons of Our Solar System Get Their Names
Most moons in our solar system are named for mythological characters from a wide variety of cultures. Uranus is the exception. Uranus' moons are named for characters in William Shakespeare's plays and from Alexander Pope's poem "Rape of the Lock." Moons are given provisional designations such as S/2009 S1, the first satellite discovered at Saturn in 2009. The International Astronomical Union approves an official name when the discovery is confirmed.

Significant Date
Huygens' image of Titan surface.
The rocks are about the size of pebbles.
  • 1610: Galileo Galilei and Simon Marius independently discover four moons orbiting Jupiter. The moons are known as the Galilean satellites in honor of Galileo's discovery, which also confirms the planets in our solar system orbit the sun.

  • 1877: Asaph Hall discovers Mars' moons Phobos and Deimos.

  • 1969: Astronaut Neil Armstrong is the first of 12 men to walk on the surface of Earth's Moon.
  • 1980: Voyager 1 instruments detect signs of surface features beneath the hazy atmosphere of Saturn's largest moon, Titan.
  • 2005: The European Space Agency's Huygens probe lands on the surface of Titan. It is the first spacecraft to successfully land on a moon beyond Earth's own moon.
  • 2000-present Using improved ground-based telescopes, orbiting observatories such as the Hubble Space Telescope and spacecraft observations, scientists find dozens of new moons in our solar system.
Moons of Our Solar System
Earth
1. Earth's Moon

Mars
2. Phobos
3. Deimos

Jupiter
4. Io
5. Europa
6. Ganymede
7. Callisto
8. Amalthea
9. Himalia
10. Elara
11. Pasiphae
12. Sinope
13. Lysithea
14. Carme
15. Ananke
16. Leda
17. Thebe
18. Adrastea
19. Metis
20. Callirrhoe
21. Themisto
22. Megaclite
23. Taygete
24. Chaldene
25. Harpalyke
26. Kalyke
27. Iocaste
28. Erinome
29. Isonoe
30. Praxidike
31. Autonoe
32. Thyone
33. Hermippe
34. Aitne
35. Eurydome
36. Euanthe
37. Euporie
38. Orthosie
39. Sponde
40. Kale
41. Pasithee
42. Hegemone
43. Mneme
44. Aoede
45. Thelxinoe
46. Arche
47. Kallichore
48. Helike
49. Carpo
50. Eukelade
51. Cyllene
52. Kore
53. Herse

Saturn
54. Mimas
55. Enceladus
56. Tethys
57. Dione
58. Rhea
59. Titan
60. Hyperion
61. Iapetus
62. Erriapus
63. Phoebe
64. Janus
65. Epimetheus
66. Helene
67. Telesto
68. Calypso
69. Kiviuq
70. Atlas
71. Prometheus
72. Pandora
73. Pan
74. Ymir
75. Paaliaq
76. Tarvos
77. Ijiraq
78. Suttungr
79. Mundilfari
80. Albiorix
81. Skathi
82. Siarnaq
83. Thrymr
84. Narvi
85. Methone
86. Pallene
87. Polydeuces
88. Daphnis
89. Aegir
90. Bebhionn
91. Bergelmir
92. Bestla
93. Farbauti
94. Fenrir
95. Fornjot
96. Hati
97. Hyrrokkin
98. Kari
99. Loge
100. Skoll
101. Surtur
102. Greip
103. Jarnsaxa
104. Tarqeq
105. Anthe
106. Aegaeon

Uranus
107. Cordelia
108. Ophelia
109. Bianca
110. Cressida
111. Desdemona
112. Juliet
113. Portia
114. Rosalind
115. Mab
116. Belinda
117. Perdita
118. Puck
119. Cupid
120. Miranda
121. Francisco
122. Ariel
123. Umbriel
124. Titania
125. Oberon
126. Caliban
127. Stephano
128. Trinculo
129. Sycorax
130. Margaret
131. Prospero
132. Setebos
133. Ferdinand

Neptune
134. Triton
135. Nereid
136. Naiad
137. Thalassa
138. Despina
139. Galatea
140. Larissa
141. Proteus
142. Halimede
143. Psamathe
144. Sao
145. Laomedeia
146. Neso

bye... bye...
Wassalamualaikum... Wr, Wb.



source :

Monday, February 25, 2013

Kenapa Terlihat Kilat Pada Malam Hari?

10 comments
Assalamualaikum...

Kalau kamu menyempatkan diri sejenak untuk melihat langit pada malam hari, kamu akan dengan mudah melihat kilat-kilat di angkasa meskipun cuaca sebenarnya tidak mendung dan tidak sedang akan turun hujan.
Kilat-kilat ini tidak hanya terjadi satu atau dua kali saja, bahkan anda sudah dapat melihat beberapa kilat dalam jangka waktu yang singkat saja, dan hal ini dapat terus terjadi sepanjang malam.

Gambar petir di malam hari
sumber : SXC
Fenomena apakah yang sebenarnya sedang terjadi di langit pada malam hari?
Dan apakah hal tersebut normal adanya? 

Berikut penjelasannya,
Kilat, petir atau halilintar adalah gejala alam yang biasanya muncul pada musim hujan di saat langit memunculkan kilatan cahaya sesaat yang menyilaukan.
Kilat atau petir dapat terjadi karena terdapat perbedaan muatan potensial antara awan dengan bumi atau antara awan satu dengan awan lainnya. Awan dapat memiliki muatan karena awan selalu bergerak terus menerus secara teratur, dan selama pergerakannya awan akan berinteraksi dengan awan lainnya, sehingga muatan negatif akan berkumpul pada salah satu sisi awan (atas atau bawah), sedangkan muatan positif akan berkumpul pada sisi sebaliknya. Jika perbedaan potensial antara awan satu dengan awan lainnya cukup besar, maka akan terjadi perpindahan muatan negatif (elektron) dari awan yang kelebihan muatan untuk mencapai kesetimbangan. Pada proses pembuangan muatan ini, media yang dilalui elektron adalah udara.



Ada anggapan yang keliru yang mengatakan bahwa kilat hanya terjadi di saat turun hujan. Dan berkat penjelasan di atas, kini kita menjadi tahu bahwa sebenarnya kilat dapat terjadi kapan saja asalkan terdapat perbedaan potensial antar awan, walaupun tidak ada hujan. Namun, kilat memang lebih sering terjadi pada saat hujan, dikarenakan pada saat hujan udara mengandung kadar air yang lebih tinggi dibanding biasanya, sehingga daya isolasi udara akan menurun dan menyebabkan arus lebih mudah mengalir, dimana hal ini tentu saja akan memperbesar peluang untuk terjadinya kilat.



Kesimpulan :
Seperti disebutkan sebelumnya, kilat akan terjadi saat ada perbedaan muatan antara awan satu dengan awan lainnya.
Jadi kilat bisa saja terjadi pada siang hari atau malam hari asal ada pelepasan elektron oleh awan yang berbeda muatan. Namun kilat memang cenderung lebih sering terlihat pada malam hari. Hal ini dikarenakan pada malam hari dimana tidak ada cahaya matahari, kilat akan lebih mudah terlihat karena tidak ada sumber cahaya lain di langit yang lebih terang dibanding kilat. Sedangkan pada siang hari, kilat tentu saja akan tersamarkan oleh cahaya matahari yang memiliki intensitas yang jauh lebih terang dari kilat.

Semoga bermanfaat,

Wassalamualaikum... Wr, Wb.



Referensi :
Wikipedia/Petir 
How Lightning Work 
Berbagai Hal 

Ubah Gambarmu menjadi Kode ASCII

4 comments
Assalamualaikum...

Dalam bidang ilmu komputer kita mengenal ada istilah yang disebut dengan kode ASCII.
Nah pada kesempatan kali ini, kita akan mempraktekan ASCII Art atau Seni ASCII.
Bagaimana caranya?
Langsung saja... Namun sebelumnya, saya akan menjelaskan sedikit mengenai apa itu Kode ASCII.

ASCII atau American Standard Codes for International Interchange (Kode Standar Amerika untuk Pertukaran Informasi) adalah kumpulan kode-kode yang dipergunakan untuk mempermudah interaksi antara komputer dan pengguna komputer.

Kode ASCII ini merupakan suatu standar internasional dalam kode huruf dan simbol seperti Hex dan Unicode tetapi ASCII lebih bersifat universal, contohnya 124 adalah untuk karakter “|”. Ia selalu digunakan oleh komputer dan alat komunikasi lain untuk menunjukkan teks. Kode ASCII sebenarnya memiliki komposisi bilangan biner sebanyak 8 bit. Dimulai dari 00000000 hingga 11111111. Total kombinasi yang dihasilkan sebanyak 256, dimulai dari kode 0 hingga 255 dalam sistem bilangan Desimal.

Seni ASCII (ASCII Art) adalah suatu bentuk karya seni yang dibuat dari karakter-karakter ASCII. Karakter ASCII tersebut dirangkai sedemikian rupa sehingga menyerupai bentuk tertentu atau tulisan tertentu.

Fungsi kode ASCII digunakan untuk mewakili karakter-karakter angka, huruf, simbol, karakter grafis maupun kode komunikasi didalam komputer.
Contoh seperti yang terlihat pada gambar berikut ini :


Nah itulah sedikit mengenai pengertian dan fungsi Kode ASCII.
Dan dibawah ini adalah cara mudah untuk mengubah gambar/foto kamu menjadi kode ASCII :

1. Silahkan kunjungi www.photo2text.com
2. Setelah muncul halaman utama dari website Photo2Text tersebut, upload foto kamu yang akan diubah ke dalam Kode ASCII dengan menekan tombol "Telusuri".
3. Tekan tombol "Submit"
Dan dengan sekejap, foto kamu akan berubah menjadi kode ASCII 
4. Pada bagian "Please Enter A Nickname" beri Nama untuk menandai gambar tersebut
5. Klik tombol "Submit".
6. Brightness pada bagian Brightness Adjustment dan jenis karakter/huruf yang dipakai pada bagian Character Set, dapat diatur sesuai keinginan kamu
7. Klik tombol "Download Now".
8. Selesai...
Hasil gambar yang telah di download tadi dapat dibuka melalui program Notepad. 
Untuk mengubahnya kedalam format jpg, kamu bisa memanfaatkan fungsi Snipping Tools (atau tekan tombol "PrtSc SysRq" pada keyboard lalu paste di Paint, lalu simpan gambar) pada komputer kamu.

Dibawah ini adalah foto saya sebelum diubah ke dalam kode ASCII, 
hehehh...maaf gak bermaksud narsis :


Dan berikut setelah diubah ke dalam kode ASCII :


Keren kaaan... hasil seni ASCII nya? Pokoknya i love ASCII Art...
Penasaran pengen nyoba?, silahkan... selamat berkarya seni dengan kode ASCII

Wassalamualaikum... Wr, Wb.

Saturday, February 23, 2013

Energy, Momentum and Work

14 comments
Assalamualaikum...

Hey guys... how are you today?
i hope you all have a wonderful day...

Ok, now we will talk about phiysic. Yes, let's talking about energy, momentum and work.

ENERGY
Energy Transformation.
In a typical lightning strike, 500 megajoules of
electric potential energy are converted
into 500 megajoules (total)
of light energy, sound energy, thermal energy,
and so on.
Energy is the ability to do work. 
For example, it takes work to drive a nail into a piece of wood—a force has to push the nail a certain distance, against the resistance of the wood.  A moving hammer, hitting the nail, can drive it in.  A stationary hammer placed on the nail does nothing.  The moving hammer has energy—the ability to drive the nail in—because it’s moving.
This hammer energy is called “kinetic energy”.  Kinetic is just the Greek word for motion, it’s the root word for cinema, meaning movies. 

Another way to drive the nail in, if you have a good aim, might be to simply drop the hammer onto the nail from some suitable height.  By the time the hammer reaches the nail, it will have kinetic energy.  It has this energy, of course, because the force of gravity (its weight) accelerated it as it came down.  But this energy didn’t come from nowhere.  Work had to be done in the first place to lift the hammer to the height from which it was dropped onto the nail.  In fact, the work done in the initial lifting, force x distance, is just the weight of the hammer multiplied by the distance it is raised, in joules.  But this is exactly the same amount of work as gravity does on the hammer in speeding it up during its fall onto the nail.  Therefore, while the hammer is at the top, waiting to be dropped, it can be thought of as storing the work that was done in lifting it, which is ready to be released at any time.  This “stored work” is called potential energy, since it has the potential of being transformed into kinetic energy just by releasing the hammer. 

To give an example, suppose we have a hammer of mass 2 kg, and we lift it up through 5 meters.  The hammer’s weight, the force of gravity, is 20 newtons (recall it would accelerate at 10 meters per second per second under gravity, like anything else) so the work done in lifting it is force x distance = 20 x 5 = 100 joules, since lifting it at a steady speed requires a lifting force that just balances the weight.  This 100 joules is now stored ready for use, that is, it is potential energy.  Upon releasing the hammer, the potential energy becomes kinetic energy—the force of gravity pulls the hammer downwards through the same distance the hammer was originally raised upwards, so since it’s a force of the same size as the original lifting force, the work done on the hammer by gravity in giving it motion is the same as the work done previously in lifting it, so as it hits the nail it has a kinetic energy of 100 joules.  We say that the potential energy is transformed into kinetic energy, which is then spent driving in the nail. 

We should emphasize that both energy and work are measured in the same units, joules.  In the example above, doing work by lifting just adds energy to a body, so-called potential energy, equal to the amount of work done. 

From the above discussion, a mass of m kilograms has a weight of mg newtons.  It follows that the work needed to raise it through a height h meters is force x distance, that is, weight x height, or mgh joules.  This is the potential energy. 

Historically, this was the way energy was stored to drive clocks.  Large weights were raised once a week and as they gradually fell, the released energy turned the wheels and, by a sequence of ingenious devices, kept the pendulum swinging.  The problem was that this necessitated rather large clocks to get a sufficient vertical drop to store enough energy, so spring-driven clocks became more popular when they were developed.  A compressed spring is just another way of storing energy.  It takes work to compress a spring, but (apart from small frictional effects) all that work is released as the spring uncoils or springs back.  The stored energy in the compressed spring is often called elastic potential energy, as opposed to the gravitational potential energy of the raised weight. 

Kinetic Energy
We’ve given above an explicit way to find the potential energy increase of a mass m when it’s lifted through a height h, it’s just the work done by the force that raised it, 
force x distance = weight x height = mgh.

Kinetic energy is created when a force does work accelerating a mass and increases its speed.  Just as for potential energy, we can find the kinetic energy created by figuring out how much work the force does in speeding up the body.

Remember that a force only does work if the body the force is acting on moves in the direction of the force.  For example, for a satellite going in a circular orbit around the earth, the force of gravity is constantly accelerating the body downwards, but it never gets any closer to sea level, it just swings around.  Thus the body does not actually move any distance in the direction gravity’s pulling it, and in this case gravity does no work on the body.

Consider, in contrast, the work the force of gravity does on a stone that is simply dropped from a cliff.  Let’s be specific and suppose it’s a one kilogram stone, so the force of gravity is ten newtons downwards.  In one second, the stone will be moving at ten meters per second, and will have dropped five meters.  The work done at this point by gravity is force x distance = 10 newtons x 5 meters = 50 joules, so this is the kinetic energy of a one kilogram mass going at 10 meters per second.  How does the kinetic energy increase with speed? Think about the situation after 2 seconds.  The mass has now increased in speed to twenty meters per second.  It has fallen a total distance of twenty meters (average speed 10 meters per second x time elapsed of 2 seconds).

So the work done by the force of gravity in accelerating the mass over the first two seconds is force x distance = 10 newtons x 20 meters = 200 joules. 

So we find that the kinetic energy of a one kilogram mass moving at 10 meters per second is 50 joules, moving at 20 meters per second it’s 200 joules.  It’s not difficult to check that after three seconds, when the mass is moving at 30 meters per second, the kinetic energy is 450 joules.  The essential point is that the speed increases linearly with time, but the work done by the constant gravitational force depends on how far the stone has dropped, and that goes as the square of the time.  Therefore, the kinetic energy of the falling stone depends on the square of the time, and that’s the same as depending on the square of the velocity.  For stones of different masses, the kinetic energy at the same speed will be proportional to the mass (since weight is proportional to mass, and the work done by gravity is proportional to the weight), so using the figures we worked out above for a one kilogram mass, we can conclude that for a mass of m kilograms moving at a speed v the kinetic energy must be:
kinetic energy = ½mv²


MOMENTUM
In a game of pool, momentum is conserved;
that is, if one ball stops dead after the collision,
the other ball will continue away with all the momentum.
If the moving ball continues or is deflected
then both balls will carry a portion of
the momentum from the collision,
At this point, we introduce some further concepts that will prove useful in describing motion.  The first of these, momentum, was actually introduced by the French scientist and philosopher Descartes before Newton.  Descartes’ idea is best understood by considering a simple example: think first about someone (weighing say 45 kg) standing motionless on high quality (frictionless) rollerskates on a level smooth floor.  A 5 kg medicine ball is thrown directly at her by someone standing in front of her, and only a short distance away, so that we can take the ball’s flight to be close to horizontal.  She catches and holds it, and because of its impact begins to roll backwards.  Notice we’ve chosen her weight so that, conveniently, she plus the ball weigh just ten times what the ball weighs by itself.

What is found on doing this experiment carefully is that after the catch, she plus the ball roll backwards at just one-tenth the speed the ball was moving just before she caught it, so if the ball was thrown at 5 meters per second, she will roll backwards at one-half meter per second after the catch.
It is tempting to conclude that the “total amount of motion” is the same before and after her catching the ball, since we end up with ten times the mass moving at one-tenth the speed.

Considerations and experiments like this led Descartes to invent the concept of “momentum”, meaning “amount of motion”, and to state that for a moving body the momentum was just the product of the mass of the body and its speed.  Momentum is traditionally labeled by the letter p, so his definition was:

momentum = p = mv

for a body having mass m and moving at speed v.  It is then obvious that in the above scenario of the woman catching the medicine ball, total “momentum” is the same before and after the catch.  Initially, only the ball had momentum, an amount 5x5 = 25 in suitable units, since its mass is 5kg and its speed is 5 meters per second.  After the catch, there is a total mass of 50kg moving at a speed of 0.5 meters per second, so the final momentum is 0.5x50 = 25, the total final amount is equal to the total initial amount.  We have just invented these figures, of course, but they reflect what is observed experimentally.

There is however a problem here—obviously one can imagine collisions in which the “total amount of motion”, as defined above, is definitely not the same before and after.  What about two people on rollerskates, of equal weight, coming directly towards each other at equal but opposite velocities—and when they meet they put their hands together and come to a complete halt?
Clearly in this situation there was plenty of motion before the collision and none afterwards, so the “total amount of motion” definitely doesn’t stay the same! In physics language, it is “not conserved”.  Descartes was hung up on this problem a long time, but was rescued by a Dutchman, Christian Huygens, who pointed out that the problem could be solved in a consistent fashion if one did not insist that the “quantity of motion” be positive.

In other words, if something moving to the right was taken to have positive momentum, then one should consider something moving to the left to have negative momentum.

With this convention, two people of equal mass coming together from opposite directions at the same speed would have total momentum zero, so if they came to a complete halt after meeting, as described above, the total momentum before the collision would be the same as the total after—that is, zero—and momentum would be conserved.

Of course, in the discussion above we are restricting ourselves to motions along a single line.  It should be apparent that to get a definition of momentum that is conserved in collisions what Huygens really did was to tell Descartes he should replace speed by velocity in his definition of momentum.  It is a natural extension of this notion to think of momentum as defined by:

momentum = mass x velocity


in general, so, since velocity is a vector, momentum is also a vector, pointing in the same direction as the velocity, of course. 

It turns out experimentally that in any collision between two objects (where no interaction with third objects, such as surfaces, interferes), the total momentum before the collision is the same as the total momentum after the collision.  It doesn’t matter if the two objects stick together on colliding or bounce off, or what kind of forces they exert on each other, so conservation of momentum is a very general rule, quite independent of details of the collision.

Momentum Conservation and Newton’s Laws

As we have discussed above, Descartes introduced the concept of momentum, and the general principle of conservation of momentum in collisions, before Newton’s time.  However, it turns out that conservation of momentum can be deduced from Newton’s laws.  Newton’s laws in principle fully describe all collision-type phenomena, and therefore must contain momentum conservation.

To understand how this comes about, consider first Newton’s Second Law relating the acceleration a of a body of mass m with an external force F acting on it:

F = ma, or force = mass x acceleration


Recall that acceleration is rate of change of velocity, so we can rewrite the Second Law:

force = mass x rate of change of velocity.

Now, the momentum is mv, mass x velocity.  This means for an object having constant mass (which is almost always the case, of course!)

rate of change of momentum = mass x rate of change of velocity. 


This means that Newton’s Second Law can be rewritten:

force = rate of change of momentum. 


Now think of a collision, or any kind of interaction, between two objects A and B, say.  From Newton’s Third Law, the force A feels from B is of equal magnitude to the force B feels from A, but in the opposite direction.  Since (as we have just shown) force = rate of change of momentum, it follows that throughout the interaction process the rate of change of momentum of A is exactly opposite to the rate of change of momentum of B.  In other words, since these are vectors, they are of equal length but pointing in opposite directions.  This means that for every bit of momentum A gains, B gains the negative of that.  In other words, B loses momentum at exactly the rate A gains momentum so their total momentum remains the same.  But this is true throughout the interaction process, from beginning to end.  Therefore, the total momentum at the end must be what it was at the beginning.

You may be thinking at this point: so what?
We already know that Newton’s laws are obeyed throughout, so why dwell on one special consequence of them?
The answer is that although we know Newton’s laws are obeyed, this may not be much use to us in an actual case of two complicated objects colliding, because we may not be able to figure out what the forces are.  Nevertheless, we do know that momentum will be conserved anyway, so if, for example, the two objects stick together, and no bits fly off, we can find their final velocity just from momentum conservation, without knowing any details of the collision.


WORK
The word “work” as used in physics has a narrower meaning than it does in everyday life.  First, it only refers to physical work, of course, and second, something has to be accomplished.  If you lift up a box of books from the floor and put it on a shelf, you’ve done work, as defined in physics, if the box is too heavy and you tug at it until you’re worn out but it doesn’t move, that doesn’t count as work.

A baseball pitcher does positive work on the ball by applying a force
to it over the distance it moves while in his grip
.
Technically, work is done when a force pushes something and the object moves some distance in the direction it’s being pushed (pulled is ok, too).  Consider lifting the box of books to a high shelf.  If you lift the box at a steady speed, the force you are exerting is just balancing off gravity, the weight of the box, otherwise the box would be accelerating.  (Of course, initially you’d have to exert a little bit more force to get it going, and then at the end a little less, as the box comes to rest at the height of the shelf.)  It’s obvious that you will have to do twice as much work to raise a box of twice the weight, so the work done is proportional to the force you exert.  It’s also clear that the work done depends on how high the shelf is.  Putting these together, the definition of work is:
work = force x distance
where only distance traveled in the direction the force is pushing counts.  With this definition, carrying the box of books across the room from one shelf to another of equal height doesn’t count as work, because even though your arms have to exert a force upwards to keep the box from falling to the floor, you do not move the box in the direction of that force, that is, upwards.

To get a more quantitative idea of how much work is being done, we need to have some units to measure work.  Defining work as force x distance, as usual we will measure distance in meters, but we haven’t so far talked about units for force.  The simplest way to think of a unit of force is in terms of Newton’s Second Law, force = mass x acceleration.  The natural “unit force” would be that force which, pushing a unit mass (one kilogram) with no friction of other forces present, accelerates the mass at one meter per second per second, so after two seconds the mass is moving at two meters per second, etc.  This unit of force is called one newton (as we discussed in an earlier lecture).  
Note that a one kilogram mass, when dropped, accelerates downwards at ten meters per second per second.  This means that its weight, its gravitational attraction towards the earth, must be equal to ten newtons.  From this we can figure out that a one newton force equals the weight of 100 grams, just less than a quarter of a pound, a stick of butter.

The downward acceleration of a freely falling object, ten meters per second per second, is often written g for short.  (To be precise, g = 9.8 meters per second per second, and in fact varies somewhat over the earth’s surface, but this adds complication without illumination, so we shall always take it to be 10.) If we have a mass of m kilograms, say, we know its weight will accelerate it at g if it’s dropped, so its weight is a force of magnitude mg, from Newton’s Second Law.

Now back to work.  Since work is force x distance, the natural “unit of work” would be the work done be a force of one newton pushing a distance of one meter.  In other words (approximately) lifting a stick of butter three feet.  This unit of work is called one joule, in honor of an English brewer.

Finally, it is useful to have a unit for rate of working, also called “power”.  The natural unit of “rate of working” is manifestly one joule per second, and this is called one watt.  To get some feeling for rate of work, consider walking upstairs.  A typical step is eight inches, or one-fifth of a meter, so you will gain altitude at, say, two-fifths of a meter per second.  Your weight is, say (put in your own weight here!) 70 kg. (for me) multiplied by 10 to get it in newtons, so it’s 700 newtons.  The rate of working then is 700 x 2/5, or 280 watts.  Most people can’t work at that rate for very long.  A common English unit of power is the horsepower, which is 746 watts. 


Exercises for the reader:  
Both momentum and kinetic energy are in some sense measures of the amount of motion of a body.  How do they differ?
Can a body change in momentum without changing in kinetic energy?
Can a body change in kinetic energy without changing in momentum?
Suppose two lumps of clay of equal mass traveling in opposite directions at the same speed collide head-on and stick to each other.  Is momentum conserved? Is kinetic energy conserved?
As a stone drops off a cliff, both its potential energy and its kinetic energy continuously change.  How are these changes related to each other?



source :
(Michael Fowler, U.  Va.  Physics, 11/29/07)

picture :