The Effectivenes of Modeling Instruction Learning on Students’ Conceptual Understanding of Rotational Dynamic

Rotational Dynamics is one of the physics topics which is quite difficult for students. Several previous studies showed students’ difficulties on this topic, one of which is the aspect of students’ conceptual understanding. Modeling instruction is the effective approach to improve students’ understanding. This model is in line with constructivist theory and cognitive model theory. This research aimed to examine the effectiveness of modeling instruction that we developed to improve students' conceptual understanding of rigid body mechanics, where the knowledge of particle mechanics serve as anchor or bridging to develop model of rigid body. This research used mixed method with embedded experimental design. It used one group pretest-posttest design and involved 65 students of a high school in Malang as the subject. Data were gathered using test consisting of 17 multiple-choice items with explanation. The students’ scores were analyzed quantitatively using t-test and N-gain to measure the improvement of students’ understanding, while the students' reasons were analyzed qualitatively. The results showed the average students’ score increased from 1.62 to 9.92 with N-gain of 0.54 (in upper medium category). We concluded that the modeling instruction was effective to improve students’ conceptual understanding.

A New Interpretation of Classical Electromagnetic Theory at the Micro Level

Because Maxwell's classical electromagnetic theory is a macroscopic electromagnetic theory, this paper attempts to establish a new theory of microscopic expression of macroscopic electromagnetic theory to compensate for the shortcomings of macroscopic electromagnetic theory at the micro level. Among them, under the microscopic electromagnetic theory system, the current will be further interpreted as the momentum flow produced by the directed collision between electrons; the charge will be further interpreted as a form of expression of electron motion; the voltage will be further interpreted as the potential difference (energy level difference) of the electron orbit. Finally, this paper successfully developed a new theory of microscopic expression of Maxwell's macroscopic electromagnetic theory by introducing microscopic atomic physics and rigid body mechanics models.

Soft-bodied terrestrial invertebrates and robots

Studies of animal locomotion and its control have generally focused on species with articulated, stiff skeletons, largely ignoring the contributions of soft tissues. Attempts to create animal-like performance in robots illustrate the limitations of using rigid-body mechanics alone. There is a growing appreciation that soft structures are critical for producing robust and adaptable behaviors in complex environments. Studies of predominantly soft animals could help to accelerate our understanding of the biomechanical role of deformable materials and their control. This chapter focuses on our current understanding of locomotion in terrestrial soft animals. It highlights the critical distinction between purely hydrostatic systems that control movements by pressurization and those that can remain relatively soft and exploit stiff substrates (the environmental skeleton strategy). The final section describes biomimetic devices that have been inspired by both animal strategies to show how such biological solutions might be employed to build controllable, highly deformable mobile machines.

Influence of Restraint Stiffness and Preload on Distribution of Reaction Loads

With recent advancements in the production of plastic materials the use of woven plastic webbings (Nylon, Polyester, etc) has increased due to decreased cost, increased load rating, greater ease of use over chains, and an increasingly proven history of use. However a common misconception is that chains and plastic webbing can be interchanged as long as the webbing has a sufficient load rating. Packages in transport are commonly secured by an arrangement of rigid blocks (chock blocks) at the base and chains, cables, or straps to the top. Analysts are apt to evaluate restraint loads by distributing the prescribed shipping loads based on relatively simple free body diagrams, assuming rigid body mechanics. However, due to the lower stiffness of plastic webbing these rigid body assumptions are not always valid, and may lead to incorrect or misleading results.