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Abstract Oblique angle collisions of two penny coins on a smooth, horizontal surface were filmed with a video camera to investigate the physics of the collision process. If one of the coins is initially at rest, then the two coins...
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Abstract Oblique angle collisions of two penny coins on a smooth, horizontal surface were filmed with a video camera to investigate the physics of the collision process. If one of the coins is initially at rest, then the two coins emerge approximately at right angles, as commonly observed in billiard ball collisions and in puck collisions on an air table. The coins actually emerged at an angle less than 90 degrees due to friction between the coins, which also resulted in both coins rotating after the collision. At glancing angles, the friction force was due to sliding friction. At other angles of incidence the coins gripped each other and the friction force was then due to static friction.
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The restitution coefficient is used to measure the energy loss between two colliding objects. It is therefore a common research topic in several fields such as physics, engineering, and medicine for which the energy behavior corre...
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The restitution coefficient is used to measure the energy loss between two colliding objects. It is therefore a common research topic in several fields such as physics, engineering, and medicine for which the energy behavior corresponding to impact is important. This topic, especially in recent years, has also begun to attract interest for applications in mining engineering, which was initially used for estimating the efficiency of impact drilling systems and later in rock fall and mill simulations. In the future, with proper consideration for measurement systems and the quantities to be determined, restitution coefficients could represent an important parameter in other research areas of mining engineering such as the prediction of blast-induced vibration, identification and evaluation of excavation systems, and rock classification. The aim of this study is to determine the values of the coefficient of restitution (COR) for various granite samples, which has been attracting the interest of researchers in mining, building, and other such sectors in recent years. Owing to this interest, the results of this study are given within the framework of research in the mining and building industries. Evaluation of the study results indicated that the COR values for various granite samples could be quickly and easily assessed, but differences between the granite samples exist. Linking the reasons for these differences with rock material specifications and forming experimental standards will promote the use of COR as an important classification and/or design parameter in those disciplines such as mining and civil engineering, which are directly interested in rock units.
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The Tightness of the Newtonian hypothesis concerning a constat value of the coefficient of restitution R has been confirmed in the paper with reference to collisions in which the loss of energy occurs in conseqence of material dam...
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The Tightness of the Newtonian hypothesis concerning a constat value of the coefficient of restitution R has been confirmed in the paper with reference to collisions in which the loss of energy occurs in conseqence of material damping. For collisions of different nature, when R depends on the density of the energy flux Φ, the paper points to the possibility of extending this notion to the case of eccentric collision. The possibility of describing R as a random function of Φ has been shown as well.
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The coefficient of restitution of soybeans impacting aluminum, glass, and acrylic was measured for drop heights of 15.1 cm, 29.2 cm, and 51.1 cm and at moisture contents of 10.7% and 15.5% (db). Statistically significant changes i...
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The coefficient of restitution of soybeans impacting aluminum, glass, and acrylic was measured for drop heights of 15.1 cm, 29.2 cm, and 51.1 cm and at moisture contents of 10.7% and 15.5% (db). Statistically significant changes in the coefficient of restitution were produced by changes in material surface, drop height and moisture content. Changes in moisture content from 10.7% to 15.5% (db) reduced the average coefficient of restitution from 0.69 to 0.59, a decrease of approximately 14%. Over the range of impact velocities tested (1.7 to 3.2 m/s produced by drops from heights from 15.1 cm to 51.1 cm) the coefficient of restitution was relatively insensitive to velocity, decreasing by less than 5% from 0.65 to 0.62. The measured values of coefficient of restitution were used as inputs to algorithms describing the behavior of a single bouncing soybean. The algorithm predicted reasonable results when compared to the observed behavior of dropped soybeans.
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The normal coefficient of restitution (COR) for a sphere that bounces obliquely or at right angles on a horizontal surface usually has an approximately constant value between 0 and 1, which are the limits for a completely inelasti...
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The normal coefficient of restitution (COR) for a sphere that bounces obliquely or at right angles on a horizontal surface usually has an approximately constant value between 0 and 1, which are the limits for a completely inelastic or a perfectly elastic collision respectively. Different results are obtained for the bounce of a non-spherical object. Measurements are presented for a double sphere consisting of two golf balls joined together, incident obliquely on a smooth horizontal surface. The COR varied from 0.15 to 1.0 depending on the alignment of the two balls and the incident spin. The results are explained in terms of a simple bounce model where the lower ball slides on the horizontal surface, and in terms of three different values of the COR defined in terms of (a) the bounce height, (b) the vertical speed of the contact point and (c) the ratio of the final to the initial kinetic energy.
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An experiment is described where a rubber ball was incident on the edge of a step to simulate the impact of a sports ball with a sharp edge. Measurements of the rebound speed, angle and spin indicated that the impact was equivalen...
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An experiment is described where a rubber ball was incident on the edge of a step to simulate the impact of a sports ball with a sharp edge. Measurements of the rebound speed, angle and spin indicated that the impact was equivalent to one with an inclined plane. The incline angle depends not only on the impact point on the ball but also on the rotation angle of the ball during the impact. Results are presented for cases where the ball was incident vertically on the step and also obliquely.
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We report on molecular dynamics simulations of oblique impacts of Lennard-Jones clusters with a weakly attractive solid surface. We confirm that the probability of adhesion to the substrate by the cluster is largely determined by ...
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We report on molecular dynamics simulations of oblique impacts of Lennard-Jones clusters with a weakly attractive solid surface. We confirm that the probability of adhesion to the substrate by the cluster is largely determined by the normal velocity of the cluster. We also analyze the dependence of the angle of reflection on the impact velocity, showing that it can be understood in terms of the velocity dependence of Newtons normal and tangential coefficients of restitution. In particular, we find that the tangential coefficient of restitution remains close to one, depending only weakly on the impact velocity, so that the angle of reflection is principally determined by the magnitude of the normal coefficient of restitution, which has a much stronger dependence on velocity. This strong velocity dependence means that at high velocities relatively small angles of reflection can occur.
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For collisions between hard bodies that have dissimilar material properties, a composite coefficient of restitution (COR) can be calculated if, for each body, the material properties and COR values for self-similar collisions are ...
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For collisions between hard bodies that have dissimilar material properties, a composite coefficient of restitution (COR) can be calculated if, for each body, the material properties and COR values for self-similar collisions are known. The composite COR represents the energy dissipated during a collision between materially-dissimilar bodies. This analysis of energy distribution during impact extends the usefulness of the measured values for COR by obtaining the separate dissipation from each body of a collision pair.
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Under the theme of collisions that occur repeatedly, we conducted easy and inexpensive experiments of rebounding spheres and Newton's cradle with two spheres to determine the coefficients of restitution using the sound record feat...
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Under the theme of collisions that occur repeatedly, we conducted easy and inexpensive experiments of rebounding spheres and Newton's cradle with two spheres to determine the coefficients of restitution using the sound record feature in modern laptops and a free and open source software called Audacity. In the rebounding sphere experiment, the coefficients of restitution of the golf and ping pong balls used were found to be 0.727 ± 0.025 and 0.816 ± 0.041 respectively. With the Netwon's cradle experiment, the coefficient of restitution of two steel sphere balls was found to be 0.987 ± 0.003. The contrasts in the results obtained from both experiments permit the operational principles of a pendulum to be emphasized, and engagements to be made to consider the transfer of kinetic energy in the form of vibrational energy of the bodies' constituents. Using a one-dimensional two-mass model with spring and damper linkages to account for harmonic motions that occur during impact, we found it possible to perform a simple analysis to account for this, and how it can be linked to high energy transfer modes such as the phenomenon of resonance and impedance matching.
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With the assumption of a linear-dashpot interaction force, the coefficient of restitution, ε_d~0(k,γ), can be computed as a function of the elastic and dissipative material constants, k and y by integrating Newton's equation of ...
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With the assumption of a linear-dashpot interaction force, the coefficient of restitution, ε_d~0(k,γ), can be computed as a function of the elastic and dissipative material constants, k and y by integrating Newton's equation of motion for an isolated pair of colliding particles. If we require further that the particles interact exclusively repulsive, which is a common assumption in granular systems, we obtain an expression ε_d~0(k,γ) which differs even qualitatively from the known result ε_d~0(k,γ). The expression ε_d~0(k,γ) allows to relate Molecular Dynamics simulations to event-driven Molecular Dynamics for a widely used collision model.
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