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Newton's graphical method for central force orbits
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| Pengarang | : | Michael Nauenberg |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 10) |
| Halaman | : | 765–771 |
| Abstrak | : | In the Principia, Book 1, Proposition 1, Newton gave a geometrical proof of angular momentum conservation for central forces. A geometrical construction associated with this proof provides a very efficient graphical method to obtain approximate orbital curves for such forces that can be traced with a ruler and a pencil. Newton's geometrical construction also satisfies a discrete form of energy conservation and it is time reversal invariant. An algorithm corresponding to this construction provides an efficient and stable numerical method to integrate the equations of motion of classical mechanics. In the past, this algorithm has been rediscovered several times without recognizing its connection to Newton's geometrical construction. |
An acoustical analogue of a galactic-scale gravitational-wave detector
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 10) |
| Halaman | : | 755–764 |
| Abstrak | : | By precisely monitoring the “ticks” of Nature's most precise clocks (millisecond pulsars), scientists are trying to detect the “ripples in spacetime” (gravitational waves) produced by the inspirals of supermassive black holes in the centers of distant merging galaxies. Here, we describe a relatively simple demonstration that uses two metronomes and a microphone to illustrate several techniques used by pulsar astronomers to search for and detect gravitational waves. An adapted version of this demonstration could be used as an instructional laboratory investigation at the undergraduate level. |
Airy wavepackets are Perelomov coherent states
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 10) |
| Halaman | : | 750–754 |
| Abstrak | : | Accelerating non-spreading wavepackets in a nonrelativistic free-particle system, with probability distribution having an Airy function profile, were discovered by Berry and Balazs [Am. J. Phys. 47(3), 264–267 (1979)], and have been subsequently realised in several optics experiments. It is shown that these wavepackets are actually Perelomov coherent states. It is found that the Galilean invariance of the Schrödinger equation plays a key role in making these states unique and gives rise to their unusual propagation properties. |
“Relativistic” particle dynamics without relativity
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 10) |
| Halaman | : | 747–749 |
| Abstrak | : | It is shown that the correct expressions for the momentum and kinetic energy of a particle moving at high speed were already implicit in physics going back to Maxwell. The demonstration begins with a thought experiment of Einstein by which he derived the inertial equivalence of energy, independently of the relativity postulates. A simple modification of the same experiment does the rest. |
UPAYA PEMERINTAH DALAM MENINGKATKAN PEMBINAAN KEARSIPAN KHUSUSNYA DI JAWA TENGAH
| Pengarang | : | Soeradi |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/31, MARET (No. 31) |
| Halaman | : | 20-30 |
| Abstrak | : | - |
Introduction to semiconductor processing: Fabrication and characterization of p-n junction silicon solar cells
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 10) |
| Halaman | : | 740–746 |
| Abstrak | : | We describe an upper-division undergraduate physics laboratory experiment that integrates the fabrication and characterization of a p-n junction in silicon. Under standard illumination, this p-n junction exhibits the photovoltaic effect as well as the typical diode rectification behavior when measured in the dark. This experiment introduces students to the physics of solar photovoltaics from the perspective of participating in the fabrication process. Procedures, experimental strategies, and typical student measurement results are presented. This low-cost, engaging, and effective lab can be adapted to undergraduate physics courses at various institutes. |
BEBERAPA PROBLEMA PADA PELAKSANAAN PENGURUSAN SURAT BERDASARKAN SISTEM KEARSIPAN KARTU KENDALI
| Pengarang | : | Budi Martono |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/31, MARET (No. 31) |
| Halaman | : | 15-19 |
| Abstrak | : | - |
Water bottle flipping physics
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 10) |
| Halaman | : | 733–739 |
| Abstrak | : | The water bottle flipping challenge consists of spinning a bottle, partially filled with water, and making it land upright. It is quite a striking phenomenon, since at first sight, it appears rather improbable that a tall rotating bottle could make such a stable landing. Here, we analyze the physics behind the water bottle flip, based on experiments and an analytical model that can be used in the classroom. Our measurements show that the angular velocity of the bottle decreases dramatically, enabling a nearly vertical descent and a successful landing. The reduced rotation is due to an increase in the moment of inertia, caused by the in-flight redistribution of the water mass along the bottle. Experimental and analytical results are compared quantitatively, and we demonstrate how to optimize the chances for a successful landing. |
PERUSAKAN ARSIP DI DAERAH TROPIS
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/31, MARET (No. 31) |
| Halaman | : | 9-14 |
| Abstrak | : | - |
PENATAAN ARSIP ELEKTRONIK (SUATU PEMIKIRAN AWAL)
| Pengarang | : | M. Irawan Wiraatmaja |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/31, MARET (No. 31) |
| Halaman | : | 1-8 |
| Abstrak | : | - |