Aspects of Force and Acceleration in Special Relativity

In relativistic dynamics, the direction of acceleration is not generally parallel to the direction of force. Both the magnitude and direction of an object’s three-acceleration can alter even when the magnitude of the applied three-force is constant. Graphs of the variation in acceleration and the angles between an object’s velocity, acceleration, and the applied force vectors are presented in order to illustrate the behavior at close to the speed of light.

Investigation of the Force Vectors Acting on the Potato in the Clamping Finger Type Dosing System of a Potato Planter

The operational accuracy of the dosing system of the potato planting machine influences the planting plant spacing, and indirectly the crop yield. The operating accuracy depends on the design of the dosing system, its kinematics and the forces acting on the planting tubers. This dissertation presents the force vectors acting on the potato in the dosing system of the guided clamping finger type potato planting machine and their spatial motion during the dosing process. Examination of the vectors reveals the improved possibilities of tuber fixation.

Research on Vibration Suppression Method Based on Coaxial Stacking Measurement

A dynamic analysis model of the unbalanced vibration response of a single-rotor system is established to study the corresponding mechanism of the unbalanced excitation force and vibration response caused by the deviation of the rotor mass centroid in this paper, and finally to achieve the combined rotor vibration suppression. First, the installation of multi-stage rotors during vibration was studied, and the rotor mass centroid transfer model in the rotating coordinate system was established to obtain the unbalanced excitation force vectors of the rotors at all levels based on the traditional stacking assembly method and axiality measurement. Second, the rotor unbalance excitation force vectors were substituted at all levels to establish the finite element analysis model of the single-rotor system. Finally, a simulation analysis was carried out for the stacking assembly of the three-stage rotor, and the rotor test piece was used for the vibration experiment. The results show that the optimal assembly phase of the multi-stage rotor obtained by the dynamic analysis model of the unbalanced vibration response of the single-rotor system can effectively suppress the vibration of the combined rotor.

Force Evaluation of Tendon Routing for Underactuated Grasping

While the modelling analysis of the kinetostatic behaviour of underactuated tendon-driven robotic fingers has been largely addressed in the literature, tendon routing is often not considered by these theoretical models. Tendon routing path plays a fundamental role in defining joint torques, and subsequently the force vectors produced by the phalanxes. However, dynamic tendon behaviour is difficult to predict and is influenced by many external factors including tendon friction, the shape of the grasped object, the initial pose of the fingers, and finger contact points. In this paper, we present an experimental comparison of the force performance of nine fingers, with different tendon routing configurations. We use the concept of force-isotropy, in which forces are equal and distributed on each phalanx as the optimum condition for an adaptive grasp. Our results show only some of the finger designs surveyed exhibited a partial adaptive behaviour, showing distributed force for the proximal and distal phalanxes throughout grasping cycles, while other routings resulted in only a single finger remaining in contact with the object.

Much Ado About Nothing: The Mental Representation of Omissive Relations

When the absence of an event causes some outcome, it is an instance of omissive causation. For instance, not eating lunch may cause you to be hungry. Recent psychological proposals concur that the mind represents causal relations, including omissive causal relations, through mental simulation, but they disagree on the form of that simulation. One theory states that people represent omissive causes as force vectors; another states that omissions are representations of contrasting counterfactual simulations; a third argues that people think about omissions by representing sets of iconic possibilities – mental models – in a piecemeal fashion. In this paper, we tease apart the empirical predictions of the three theories and describe experiments that run counter to two of them. Experiments 1 and 2 show that reasoners can infer temporal relations from omissive causes – a pattern that contravenes the force theory. Experiment 3 asked participants to list the possibilities consistent with an omissive cause – it found that they tended to list particular privileged possibilities first, most often, and faster than alternative possibilities. The pattern is consistent with the model theory, but inconsistent with the contrast hypothesis. We marshal the evidence and explain why it helps to solve a long-standing debate about how the mind represents omissions.

Much ado about nothing: The mental representation of omissive relations

When the absence of an event causes some outcome, it is an instance of omissive causation. For instance, not eating lunch may cause you to be hungry. Recent psychological proposals concur that the mind represents causal relations, including omissive causal relations, through mental simulation, but they disagree on the form of that simulation. One theory states that people represent omissive causes as force vectors; another states that omissions are representations of contrasting counterfactual simulations; a third argues that people think about omissions by representing sets of iconic possibilities – mental models – in a piecemeal fashion. In this paper, we tease apart the empirical predictions of the three theories and describe experiments that run counter to two of them. Experiments 1 and 2 show that reasoners can infer temporal relations from omissive causes – a pattern that contravenes the force theory. Experiment 3 asked participants to list the possibilities consistent with an omissive cause – it found that they tended to list particular privileged possibilities first, most often, and faster than alternative possibilities. The pattern is consistent with the model theory, but inconsistent with the contrast hypothesis. We marshal the evidence and explain why it helps to solve a long-standing debate about how the mind represents omissions.

Basic background: Everyday physics and its math

Chapter 2 introduces portions of mathematics that underly the physics of ordinary objects and experience, leading to discussions of atoms and electrons as elementary particles, to aggregates that exhibit ows and waves, to concepts of force, vectors, energy and their equations of change. It notes the defining properties of light beams, distinguishes coherent and incoherent sources, and raises the question of radiation granules as photons.