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Theoretical study of the geometrical non-linearity of the elastic properties of helical springs
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| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 958-961 |
| Abstrak | : | We give a detailed derivation of the equation describing the elastic properties of the helical springs in the case of their large deformations. It is shown that the Taylor expansion for the restoring force contains, in addition to a linear term, a term quadratic in the strain. We discuss the physical consequences of this term. A surprising example of this is that for large values of the initial pitch angle during compression of spring, there may be an interval of strain values, for which the differential stiffness becomes negative. The issues outlined in this article will be useful for instructors and advanced undergraduates who deal with modern elasticity theory. |
Collecting data with a mobile phone: Studies of mechanical laws such as energy and momentum conservation
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 948-957 |
| Abstrak | : | We use videos taken with a mobile phone to study conservation of energy, conservation of momentum, and the work-energy theorem by analyzing the collision of a cue ball and the eight ball. A video of the full time sequence, starting from before the cue ball is struck until well after the collision, is recorded with a mobile phone. The video is imported into Origin (free to teachers and students taking a class) [OriginLab Corporation, Origin, Version 2020 (OriginLab Corporation, Northampton, MA, USA, 2020)], where the coordinates of the balls are digitized frame-by-frame using the free Video Extractor app. From these data, the velocities are determined as a function of time and used to determine the energy and momentum of each ball. The data suggest that the balls slip through part of their motion when rotating at an angular velocity different than the rolling angular velocity, so angular momentum and frictional torque must be considered. Such experiments require no specialized equipment other than a device to take a video, and the act of digitizing the data provides the student with visual reinforcement of the physics. Experimentation by students outside of campus can be fun for them and provides a useful alternative to classes when in-lab experiments are not practical. Use of a mobile phone in this way is generally applicable to any other mechanical phenomena that involve motion. |
PERANAN KANTOR ARSIP DAERAH PROPINSI DAERAH TINGKAT I JAWA BARAT
| Pengarang | : | Ariail, Donald L.,Smalt, Steven W.,Quosigk, Benedikt M. |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/34, DESEMBER-MARET (No. 34) |
| Halaman | : | 36-47 |
| Abstrak | : | - |
Flight and bounce of spinning sports balls
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 934-947 |
| Abstrak | : | Standard university or high-school physics teaching material on projectile motion is usually based on Newton's second law in vacuum, neglecting aerodynamics. We present a low-cost experiment for teaching projectile motion using the students' cell phones and sports equipment, which allows the students to test theory and numerical simulation against experimental data in the real world. For a shot put, theoretical predictions assuming projectile motion in vacuum agree with experimentally obtained trajectories in air to within a few centimeters. However, for a table tennis ball, vacuum trajectories can be almost three times as long as experimentally obtained trajectories. An equation of motion including the aerodynamic drag force has no analytic solution, but it is straightforward to integrate numerically for high-school or first-year university students. Accounting for aerodynamic drag substantially improves the match with experimental data for any ball. In a second experiment, balls are shot with spin resulting in curveball trajectories. Numerical simulations including the Magnus force can give accurate predictions of 3D curveball trajectories, both curving according to the normal and the inverse Magnus effect. Balls shot with topspin and backspin are also accurately modelled. Finally, we model the bounce of an arbitrarily spinning ball using linear and angular impulse-momentum theorems and coefficients of restitution in vertical and horizontal directions. We find agreement with experimental data to within centimeters. |
HUBUNGAN TATA PERSURATAN DENGAN MANAJEMEN KEARSIPAN DALAM PROSPEKTIF
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/34, DESEMBER-MARET (No. 34) |
| Halaman | : | 11-35 |
| Abstrak | : | - |
MENEJEMEN KEARSIPAN DAN PENGEMBANGANNYA
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/34, DESEMBER-MARET (No. 34) |
| Halaman | : | 1-10 |
| Abstrak | : | - |
Learning-assistant-supported active-learning in a large classroom
| Pengarang | : | Vera Margoniner |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 924-933 |
| Abstrak | : | We present results and lessons learned from a Learning Assistant (LA) program combined with flipped classroom delivery and team learning in our calculus-based, introductory physics (mechanics) courses at California State University, Sacramento. A primarily undergraduate institution, our university serves a largely underprivileged student population, with one half of students coming from low-income households and one third being first-generation college students. We describe our setup in detail and analyze data from 13 classes, four instructors, and 43 learning assistants. We find that (1) learning gains for LA supported classes are on average twice as large as our traditionally taught classes; (2) learning gains are dependent on pre-test scores; and (3) they are also dependent on participation rates. We also analyze student and LA responses to end of semester surveys. Two-thirds of the students self-report that their study skills have improved from taking the LA-supported class, and their comments on course structure are overall positive. Over 90% of the LAs have very positive views of the program, and it is especially rewarding to see that 73% of the LAs who had not previously considered teaching as a career became more interested after participating in the program. |
A LEGOTM dynamic force “macroscope”
| Pengarang | : | D. Taylor |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 906-917 |
| Abstrak | : | We describe the design, construction, and operation of a LEGOTM model of a dynamic force microscope, using magnetic forces as an analog of interatomic interactions. The macroscope provides key insights into the operating principles of frequency modulated non-contact atomic force microscopy—currently the scanning probe technique of choice for maximal (i.e., submolecular) spatial resolution—and is, therefore, particularly suited as a project or demonstration for nanoscience education at the undergraduate or postgraduate level. |
PROSEDUR KERJA KANTOR ARSIP DAERAH
| Pengarang | : | Mian |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/33, AGUSTUS-NOPEMBER (No. 33) |
| Halaman | : | 56-65 |
| Abstrak | : | - |
KEBIJAKSANAAN KEARSIPAN PADA JAJARAN PEMERINTAH DAERAH TINGKAT I SULAWESI SELATAN
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/33, AGUSTUS-NOPEMBER (No. 33) |
| Halaman | : | 47-55 |
| Abstrak | : | - |