Failed Russian Mars Probe May Crash in Indian Ocean Sunday

by Mike Wall, SPACE.com Senior Writer

Date: 11 January 2012 Time: 05:45 PM ET

A doomed Russian Mars probe that's been stuck in Earth orbit for two months may finally come crashing down Sunday (Jan. 15) over the Indian Ocean, Russian space officials say.

The 14.5-ton Phobos-Grunt spacecraft should fall back to Earth sometime between Saturday and Monday (Jan. 14 to Jan. 16), Russia's Federal Space Agency, known as Roscosmos, announced in a statement today (Jan. 11).

If Phobos-Grunt comes down at the "central point" in that window — 4:18 a.m. EST (0918 GMT) on Sunday — it will fall over a stretch of empty ocean west of the Indonesian island of Java, according to a re-entry projection map Roscosmos published with the update.

But these projections are far from set in stone. The predicted time and place of re-entry may change as engineers continue to track the spacecraft's decaying orbit, officials said. All that's known for sure is that Phobos-Grunt will come down somewhere between 51 degrees north latitude and 51 degrees south latitude. [Photos of the Phobos-Grunt mission]

Falling back to Earth

Phobos-Grunt launched Nov. 8 on a mission to collect soil samples from the Mars moon Phobos and return them to Earth ("grunt" means "soil" in Russian). However, the probe's main engines failed to fire as planned to send it toward Mars, and the craft got stuck orbiting Earth.

Russian officials still aren't sure what caused the failure. They recently raised the possibility that some form of sabotage may have crippled Phobos-Grunt and doomed its $165 million mission.

The spacecraft has been spiraling lower and lower for months, on an inevitable collision course with Earth's atmosphere. The minimum altitude of Phobos-Grunt's orbit as of today is about 106 miles (171 kilometers), according to Roscosmos.

The huge probe is carrying about 7.5 tons of toxic hydrazine fuel, prompting some observers to worry about potential environmental impacts of the probe's looming re-entry. Russian space officials have repeatedly dismissed those concerns, however, saying that the fuel — which is encased in an aluminum tank — should burn up high in Earth's atmosphere.

Most of Phobos-Grunt should meet that same fate. Experts predict that just 20 to 30 pieces, weighing a maximum of 440 pounds (200 kilograms) in total, will actually hit the Earth.

Phobos-Grunt's demise comes close on the heels of two other uncontrolled satellite falls recently. NASA's 6.5-ton UARS climate satellite re-entered over the Pacific Ocean in September, and Germany's 2.7-ton ROSAT satellite crashed over the Indian Ocean a month later.

Both the UARS and ROSAT re-entries were expected, however, and the two satellites had long since completed their primary science missions. No one on the ground was hurt in either instance.

http://www.space.com/14215-phobos-grunt-mars-probe-crash-indian-ocean.html

Soal Latihan Ujian Nasional IV IPA SMP 2010/2011

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Jumlah Planet di Tata Surya Akan Berkurang

VIVAnews - Tahun 2006 lalu, International Astronomical Union (IAU) mendegradasi Pluto dari planet menjadi sebuah planet kerdil (dwarf planet). Alasannya, dari sisi ukuran, Pluto tidak memenuhi syarat sebagai untuk disebut sebagai sebuah planet.

Saat ini sistem tata surya tinggal memiliki delapan planet yang mengelilingi Matahari. Akan tetapi, dari bukti-bukti baru yang ditemukan, ke depannya bisa jadi tata surya hanya akan terdiri dari 7 buah planet saja.

Dari sisi ukuran, Merkurius memang dua kali lebih besar dibanding Pluto. Namun ternyata, Merkurius, yang kini menjadi planet terkecil yang ada di tata surya itu juga semakin menciut.

Peneliti memperkirakan, Merkurius memang tidak akan jadi sekecil mantan planet kesembilan milik tata surya. Akan tetapi jika ukurannya terus mengecil, IAU tentu akan mendegradasi status planet itu.

Penyebab menciutnya ukuran Merkurius adalah karena inti planet itu yang terdiri dari zat besi cair terus mendingin dan memadat sehingga menciutkan ukuran planet itu dari dalam. Menurut peneliti, pergerakan ini sudah berlangsung sejak miliaran tahun yang lalu.

Penciutan Merkurius juga terlihat dari foto-foto milik satelit Messenger milik NASA yang menggambarkan terjadi lipatan di kerak planet itu. Dari foto juga terungkap bahwa dulu, Merkurius punya banyak gunung berapi yang meletus. Adapun yang mematikan gunung itu adalah karena inti planet semakin dingin.

“Merkurius menunjukkan pada kita berapa besar pengaruh pendinginan inti planet terhadap evolusi yang terjadi di permukaan,” kata Sean Solomon, peneliti dari Carnegie Institution for Science, di Washington, seperti dikutip dari LA Times, 28 Desember 2010.

Sama seperti Mars dan Bulan, Merkurius sangat berapi saat ia lahir. Namun planet itu kehilangan panasnya sejalan dengan pertumbuhannya selama sekitar 4,5 miliar tahun terakhir yang menghentikan aktivitas vulkanik di sana.

Sebagai informasi, planet Bumi juga mengalami pendinginan dengan cara yang serupa. Dan dalam waktu beberapa miliar tahun mendatang, Bumi juga akan terlalu dingin untuk gunung berapi. Setelah inti bumi semakin dingin, gunung-gunung berapi di Bumi akan berhenti meletus. (umi)

• VIVAnews

Pesawat Bisa Sebabkan Hujan Es atau Salju

VIVAnews - Anda pernah menyaksikan hujan salju atau hujan es turun di kota-kota atau di pelosok Indonesia? Ternyata, fenomena itu bukanlah hal yang aneh dan sudah ada penjelasannya. Ini dia.

Saat sedang duduk di kabin, dengan sandaran kursi berdiri tegak serta meja makan di hadapan Anda dalam posisi terkunci, pesawat yang Anda tumpangi bisa jadi sedang memicu kejadian tak lazim, misalnya seperti hujan es.

Andrew Heymsfield, mikrofisikawan dari National Center for Atmosfpheric Research di Boulder, Colorado, menemukan bahwa pesawat bisa menyebabkan lubang di awan dan mengubah cuaca daratan di bawahnya.

Seperti dikutip dari Discovermagazine, Senin 27 Desember 2010, kristal es tidak terbentuk dengan mudah. Sama halnya dengan titik-titik uap air yang tetap dalam bentuk asalnya, meskipun atmosfir di sekitarnya mencapai jauh di bawah titik beku.

Menurut Heymsfield, pesawat yang memasuki awan yang super dingin setelah mereka tinggal landas atau sebelum mendarat bisa menyebabkan gangguan yang dapat membekukan titik-titik uap air tersebut secara instan.

“Ketika mesin turboprop milik pesawat memaksa air di belakang sirip-sirip propeller atau ketika mesin jet menyebabkan udara lembab mengalir di bawah sayap agar memberi daya angkat pada pesawat, udara kemudian menyebar dan mendingin,” ujar Heymsfield.

Salah satu dari efek yang ditimbulkan pesawat itu, kata Heymsfield, bisa menurunkan temperatur udara hingga lebih dari satu derajat.

“Ini seketika akan membekukan titik-titik air di awan,” kata Heymsfield. “Titik air ini dengan cepat akan membentuk kristal es yang keluar dari awan sebagai salju,” ucapnya.

Heymsfield menyebutkan, fenomena ini sedikit menjelaskan terjadinya keterlambatan pesawat di musim dingin yang belakangan banyak terjadi.

“Efek utama dari kejadian ini adalah berubahnya curah hujan lokal,” tutur Heymsfield. “Di sekitar bandara, khususnya di musim dingin, lebih banyak salju yang turun dibandingkan di kawasan lain”. (art)

• VIVAnews

Making My Own Metal Detector!

Mention the words metal detector and you'll get completely different reactions from different people. For instance, some people think of combing a beach in search of coins or buried treasure. Other people think of airport security, or the handheld scanners at a concert or sporting event.

A basic metal detector consists of an electronic box and battery case on one end, with a brace or handle for the operator's arm. An insulated wire wraps around a telescoping shaft and into a round plastic disk called the coil. This disk comes off the shaft at an angle which allows it to be held parallel to the ground. The operator straps on or grips the electronic box and turns on the power. The idea is to slowly sweep the coil end over the ground until an electronic signal is heard. This lets the user know that some metallic element is buried directly beneath the area swept by the coil.

Metal detectors work on the principal of electromagnetics and their effects on conductive metals. There are actually two separate elements in the coil of a typical unit. One is a high-powered coil of metal which uses the battery power to generate a penetrating magnetic field. This coil is called the transmitter. As the elecromagnetic field enters the ground, anything metallic will become charged with magnetism, similar to a paper clip become magnetized after contact with a standard bar magnet.

Michael FARADAY observed (1831) that when a magnet is moved through a closed coil of wire, a current is induced in the wire. The direction of the current flow is such as to create a magnetic field opposite in direction to that of the change in the field produced by the magnet. Faraday then replaced the magnet with an electromagnet.

Two coils were wound close together, the first being connectedto a battery and the second to a galvanometer, which measures small currents.

Metal detectors must also be adjusted to eliminate false positives generated by natural deposits of metal in the soil or sand itself. Most units allow users to change the sensitivity of the coil in order to cancel out the background clutter. Some other uses of metal detecting technology include security inspections at airports, government buildings and other public places. Construction crews and woodworkers also use hand-held metal detectors to find dangerous nails or other metallic debris in reclaimed building materials and trees.

Soal Latihan Ujian Nasional IPA SMP 2010/2011

SMP Negeri 7 Salatiga telah mengadakan Latihan Ujian Nasional pada 25-29 November 2010 pada mata pelajaran bahasa Inggris, bahasa Indonesia, matematika dan IPA.



Soal latihan ujian nasional 2010/2011 mata pelajaran IPA Fisika SMP dapat diunduh di sini.

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Draft SKL Ujian Nasional IPA Fisika SMP 2011

Standar kompetensi Lulusan (SKL) IPA
Ujian Nasional SMP tahun 2011

1.Melakukan pengukuran dasar secara teliti dengan menggunakan alat ukur yang sesuai dan sering digunakan dalam kehidupan sehari-hari.
a) Menentukan besaran fisika dan satuan yang sesuai
b) membaca alat ukur

2. Menerapkan konsep zat dan kalor serta kegunaannya dalam kehidupan sehari-hari
a) Menentukan salah satu variabel dari rumus p = V/m
b) Menjelaskan pengaruh suhu dan pemuaian dalam kehidupan sehari-hari
c) Menentukan salah satu variabel dari rumus kalor

3. menjelasskan dasar-dasar mekanika (gerak, gaya, dan energi) serta penerapannya dalam kehidupan sehari-hari.
a) membedakan jenis gerak lurus dan mengidentifiikasi terjadinya gerak tersebut dalam kehidupan sehari-hari
b) menentukan variabel dari rumus tekanan pada suatu zat
c) menyebutkan perubahan energi pada suatu alat dalam kehidupan sehari-hari
d) menentukan besaran fisika pada usaha dan energi
e) mengidentifikasi jenis-jenis peswat sederhana serta penerapannya dalam kehidupan sehari-hari

4. memahami konsep-konsep dan penerapan, getaran, gelombang, bunyi, dan optik dalam produk teknologi sehari-hari
a) menentukan salah satu besaran fisika pada getaran dan gelombang
b) menjelaskan ciri dan sifat-sifat bunyi serta pemanfaatannya
c) menentukan berbagai besaran fisika jika benda diletakkan di depan lensa atau cermin
d) menentukan besaran-besaran pada alat optik dan penggunaannya dalam kehidupan sehari-hari

5. memahami konsep kelistrikan dan kemagnetan serta penerapannya dalam kehidupan sehari-hari
a) menjelaskan terjadinya gejala listrik statis serta menentukan jenis muatan
b) menentukan besaran fisika pada berbagai bentuk rangkaian listrik
c) menentukan besarnya energi dan daya listrik dalam kehidupan sehari-hari
d) menjelaskan cara pembuatan magnet serta menentukan kutub-kutub yang dihasilkan

6. memahami sistem tata surya dan proses yang terjadi didalamnya
a) menjelaskan karakteristik benda-benda langit dalam tata surya
b) menjelaskan keterkaitan pasang naik dan pasang surut dengan posisi bulan

Peta Konsep (Concept Maps)

Learning physics by concept maps.
Belajar Fisika melalui peta konsep.

HyperPhysics





Concept maps in physics:
Peta konsep dalam fisika:

1. Electricity and magnetism (Kelistrikan dan kemagnetan)

2. Mechanics (Mekanika)

3. Heat and thermodynamics (Kalor dan termodinamika)

4. Condensed Matter (Zat Padat)

5. Nuclear Physics (Fisika Inti)

6. Quantum Physics (Fisika kuantum)

7. Astrophysics

8. Relativity (relativitas)

9. Sound and hearing (Bunyi)

10. Light and vision (Cahaya)

Barometer

The following is a question on a physics exam at the University of Copenhagen:

"Describe how to determine the height of a skyscraper with a barometer."
One student replied: "You tie a long piece of string to the neck of the barometer, then lower the barometer from the roof of the skyscraper to the ground. The length of the string plus the length of the barometer will equal the height of the building."

This highly original answer so incensed the examiner that he failed the student who immediately appealed on the grounds that his answer was indisputably correct.

The university appointed an independent arbiter to decide the case.

The arbiter ruled that the answer was indeed correct, but did not display any noticeable knowledge of physics. It was decided to call the student in and allow him six minutes in which to provide a verbal answer which showed at least a minimal familiarity with the basic principles of physics.

For five minutes the student sat in silence, forehead creased in thought. The arbiter reminded him that time was running out, to which the student replied that he had several extremely relevant answers, but couldn't make up his mind which to use.

On being advised to hurry up the student replied: "First, you could take the barometer up to the roof of the skyscraper, drop it over the edge, and measure the time it takes to reach the ground. The height of the building can then be worked out from this formula I have worked out for you on my text paper here."

Then the student added, "But, Sir, I wouldn't recommend it. Bad luck on the barometer."

"Another alternative", offered the student, "is this: If the sun is shining you could measure the height of the barometer,then set it on end and measure the length of its shadow. Then you measure the length of the skyscraper's shadow, and thereafter it is a simple matter of proportional geometry to work out the height of the skyscraper. On the paper is the formula for that as well."

"But, Sir, if you wanted to be highly scientific about it, you could tie a short piece of string to the barometer and swing it like a pendulum, first at ground level and then on the roof of the skyscraper. The height is worked out by the difference in a gravitational formula, which I have determined here this time on a long sheet of paper with a very long and complicated calculation."

"Or, Sir, here's another way, and not a bad one at all. If the skyscraper has an outside emergency staircase, it would be easier to walk up it and mark off the height of the skyscraper in barometer lengths, then add them up."

"But if you merely wanted to be very boring and very orthodox about the answer you seem to seek, of course, you could use the barometer to measure the air pressure on the roof, and on the ground, and then convert the difference in millibars into feet to give the height of the building."

"But since we are constantly being exhorted to exercise independence of mind and apply scientific methods, undoubtedly the best way would be to knock on the janitor's door and say to him 'If you would like a nice new barometer, I will give you this one if you tell me the height of this skyscraper'."

The student was Niels Bohr, the only Dane ever to win the Nobel Prize in physics.

Bedanya Fisikawan dan Insinyur

Apa perbedaan antara seorang insinyur, seorang fisikawan, dan seorang matematikawan?

Jawab:

• Jika seorang insinyur berjalan memasuki sebuah ruangan, kemudian melihat api di tengah ruangan serta seember air di pojok ruangan, maka ia akan segera mengambil ember berisi air tersebut lalu menumpahkannya di tengah ruangan untuk mematikan api.

• Jika seorang fisikawan berjalan memasuki sebuah ruangan, kemudian melihat api di tengah ruangan serta seember air di pojok ruangan, maka ia akan mengambil sedikit air dalam ember tersebut lalu menuangkannya secara melingkar di sekeliling api sehingga api tersebut mati perlahan.

• Jika seorang matematikawan berjalan memasuki sebuah ruangan, kemudian melihat api di tengah ruangan serta seember air di pojok ruangan, maka ia meyakinkan dirinya bahwa di sana sudah ada solusi sehingga ia pun pergi meninggalkan ruangan begitu saja.

sumber: http://102fm- itb.org/2008/ 05/beda-insinyur -ahli-fisika- dan-matematika/

Just kidding.

Having fun.

GBU.