5. On Centrobaric Bodies

1866 ◽  
Vol 5 ◽  
pp. 190-192
Author(s):  
W. Thomson
Keyword(s):  
Rigid Body ◽  
Natural Philosophy ◽  
The Body ◽  
Centre Of Gravity ◽  
The Earth ◽  
Line Passing ◽  
Single Force

This is an abstract of an investigation which will be published in full in “Thomson and Tait's Natural Philosophy.” It contains the application of Green's wonderful results regarding the potential to the determination of the centre of gravity of a system when there is such a point. Some of the more remarkable propositions, which are thus established are as follows:—If the action of terrestrial or other gravity on a rigid body is reducible to a single force in a line passing always through one point fixed relatively to the body, whatever be its position relatively to the earth or other attracting mass, that point is called its centre of gravity, and the body is called a centrobaric body.

Chelyabinsk Meteorite

2021 ◽  
Author(s):  
Olga Popova
Keyword(s):  
Energy Deposition ◽  
Seismic Waves ◽  
The Body ◽  
Structure And Properties ◽  
Ural Mountains ◽  
Asteroid Impact ◽  
Unusual Event ◽  
The Earth ◽  
First Time

The asteroid impact near the Russian city of Chelyabinsk on February 15, 2013, was the largest airburst on Earth since the 1908 Tunguska event, causing a natural disaster in an area with a population exceeding 1 million. On clear morning at 9:20 a.m. local time, an asteroid about 19 m in size entered the Earth atmosphere near southern Ural Mountains (Russia) and, with its bright illumination, attracted the attention of hundreds of thousands of people. Dust trail in the atmosphere after the bolide was tens of kilometers long and was visible for several hours. Thousands of different size meteorites were found in the areas south-southwest of Chelyabinsk. A powerful airburst, which was formed due to meteoroid energy deposition, shattered thousands of windows and doors in Chelyabinsk and wide surroundings, with flying glass injuring many residents. The entrance and destruction of the 500-kt Chelyabinsk asteroid produced a number of observable effects, including light and thermal radiation; acoustic, infrasound, blast, and seismic waves; and release of interplanetary substance. This unexpected and unusual event is the most well-documented bolide airburst, and it attracted worldwide attention. The airburst was observed globally by multiple instruments. Analyses of the observational data allowed determination of the size of the body that caused the superbolide, its velocity, its trajectory, its behavior in the atmosphere, the strength of the blast wave, and other characteristics. The entry of the 19-m-diameter Chelyabinsk asteroid provides a unique opportunity to calibrate the different approaches used to model meteoroid entry and to calculate the damaging effects. The recovered meteorite material was characterized as brecciated LL5 ordinary chondrite, in which three different lithologies can be distinguished (light-colored, dark-colored, and impact-melt). The structure and properties of meteorites demonstrate that before encountering Earth, the Chelyabinsk asteroid had experienced a very complex history involving at least a few impacts with other bodies and thermal metamorphism. The Chelyabinsk airburst of February 15, 2013, was exceptional because of the large kinetic energy of the impacting body and the damaging airburst that was generated. Before the event, decameter-sized objects were considered to be safe. With the Chelyabinsk event, it is possible, for the first time, to link the damage from an impact event to a well-determined impact energy in order to assess the future hazards of asteroids to lives and property.

scholarly journals Rigid-Earth Nutation Models

2000 ◽  
Vol 180 ◽  
pp. 190-195
Author(s):  
J. Souchay
Keyword(s):  
Transfer Function ◽  
Rigid Body ◽  
Earth Model ◽  
High Quality ◽  
Frequency Dependent ◽  
Relative Improvement ◽  
The Earth ◽  
Rigid Earth

AbstractDespite the fact that the main causes of the differences between the observed Earth nutation and that derived from analytical calculations come from geophysical effects associated with nonrigidity (core flattening, core-mantle interactions, oceans, etc…), efforts have been made recently to compute the nutation of the Earth when it is considered to be a rigid body, giving birth to several “rigid Earth nutation models.” The reason for these efforts is that any coefficient of nutation for a realistic Earth (including effects due to nonrigidity) is calculated starting from a coefficient for a rigid-Earth model, using a frequency-dependent transfer function. Therefore it is important to achieve high quality in the determination of rigid-Earth nutation coefficients, in order to isolate the nonrigid effects still not well-modeled.After reviewing various rigid-Earth nutation models which have been established recently and their relative improvement with respect to older ones, we discuss their specifics and their degree of agreement.

On the harmonic oscillations of a rigid body on a free surface

1965 ◽  
Vol 21 (3) ◽  
pp. 427-451 ◽  
Author(s):  
W. D. Kim
Keyword(s):  
Integral Equation ◽  
Free Surface ◽  
Rigid Body ◽  
Potential Problem ◽  
Harmonic Oscillation ◽  
Added Mass ◽  
The Body ◽  
Rigorous Solution ◽  
Damping Coefficients

The present paper deals with the practical and rigorous solution of the potential problem associated with the harmonic oscillation of a rigid body on a free surface. The body is assumed to have the form of either an elliptical cylinder or an ellipsoid. The use of Green's function reduces the determination of the potential to the solution of an integral equation. The integral equation is solved numerically and the dependency of the hydrodynamic quantities such as added mass, added moment of inertia and damping coefficients of the rigid body on the frequency of the oscillation is established.

scholarly journals Urgensi dan Legitimasi Fatwa Majelis Permusyawaratan Ulama Aceh Nomor 3 Tahun 2018 tentang Penetapan Arah Kiblat

2020 ◽  
Vol 14 (1) ◽  
pp. 87-98
Author(s):  
Ismail Ismail
Keyword(s):  
Focus Of Attention ◽  
The Body ◽  
The Earth ◽  
Science Technology

When Muslims have settled on the earth, one of the problems which become a focus of attention is the Kiblah direction. For Muslims, the Kiblah direction is not only the need for prayer which is one of the legitimate conditions of prayer, but also includes other needs related to Kiblah such as the position of burying the body, establishing a mosque and musalla. This paper explains the position of the MPU Aceh’s fatwa Number 3 of 2018 concerning the determination of the direction of the MUI of the fatwa of MUI number 3 and 5 of 2010 concerning the direction of Kiblah and explaining its relevance to the context. With the approach of astronomy, the position of the MPU Aceh fatwa Number 3 of 2018 concerning the determination of the direction of Kiblah is complementary to the MUI fatwa Number 3 and 5 of 2010 concerning the Kiblah direction. Improvements to the integrity and intensity of fatwas are responsive, proactive and anticipatory. The presence of the MPU Aceh’s fatwa on Kiblah direction is able to solve the problem of Kiblah direction in Indonesia, both in the technical and the sociological domain, because the content of the fatwa is relevant with the context and it accommodates the dimensions of science, technology and Fiqh as a characteristic of collective diligence (Ijtihad Jama'i).

scholarly journals DESCRIPTIONS OF A FEW LEAF-EATING COLEOPTEROUS LARVÆ

1883 ◽  
Vol 15 (2) ◽  
pp. 21-23
Author(s):  
D. W. Coquillett
Keyword(s):  
Colorado Potato Beetle ◽  
The Body ◽  
The Earth ◽  
Potato Beetle ◽  
The One

The following larvæ (with the exception of the one first described) have the usual Chrysomelid form of which the well-known Colorado Potato Beetle may be taken as a type. In Chrysomela pallida, Say, the body is more elongate, approaching the Coccinellidœ somewhat in form. With the exception of Lema collaris, Say, which forms a sort of cocoon among the leaves, they all enter the earth to pupate. A few of the following larvæ have been described by various authors, and are introduced here merely for comparison.Chrysomela pallida, Say. Body black, elongated, much wrinkled and roughened; the sutures of the segments and the venter sometimes tinged with brown; head and cervical shield polished black; length 8 mm. Lives in communities on poplar. Several of these larvæ entered the earth to pupate June 1st, and the beetles issued about June 19th. (Determination of Dr. Horn.)

On Dynamically Equivalent Force Systems and Their Application to the Balancing of a Broom or the Stability of a Shoe Box

2004 ◽  
Author(s):  
Just L. Herder ◽  
Arend L. Schwab
Keyword(s):  
Rigid Body ◽  
Center Of Mass ◽  
The Body ◽  
Resultant Force ◽  
Dynamic Equivalence ◽  
Force Systems ◽  
The Stability ◽  
Metacentric Height ◽  
The Given

The stability of a rigid body on which two forces are in equilibrium can be assessed intuitively. In more complex cases this is no longer true. This paper presents a general method to assess the stability of complex force systems, based on the notion of dynamic equivalence. A resultant force is considered dynamically equivalent to a given system of forces acting on a rigid body if the contributions to the stability of the body of both force systems are equal. It is shown that the dynamically equivalent resultant force of two given constant forces applies at the intersection of its line of action and the circle put up by the application points of the given forces and the intersection of their lines of action. The determination of the combined center of mass can be considered as a special case of this theorem. Two examples are provided that illustrate the significance of the proposed method. The first example considers the suspension of a body, by springs only, that is statically balanced for rotation about a virtual stationary point. The second example treats the roll stability of a ship, where the metacentric height is determined in a natural way.

scholarly journals Experimental Determination of Rigid Body Properties: An Evaluation on the Use of Piezoelectric or MEMS Tri-Axial Accelerometers

2018 ◽  
Vol 148 ◽  
pp. 01003 ◽  
Author(s):  
António Urgueira ◽  
Nuno Venâncio ◽  
Pedro Riscado ◽  
Raquel Almeida ◽  
Tiago Silva
Keyword(s):  
Rigid Body ◽  
Experimental Determination ◽  
Low Cost ◽  
Low Frequency ◽  
The Body ◽  
Identification Algorithm ◽  
Inertia Properties ◽  
Areas Of Interest ◽  
New Sensors

The development of new sensors that are available at more accessible prices may lead to the spread of their use on common studies in structural dynamics. One of areas of interest is the experimental determination of rigid body properties that are mandatory when the vibration response is to be calculated at low frequency ranges. In this work, a comparison of the experimental determination of rigid body properties is carried out to evaluate the performance of the commonly used tri-axial piezoelectric accelerometers and their equivalent MEMS sensors. Although their prices are quite different, both sensors can measure the inertia restraint line that is related to the inertia properties of the tested object. An identification algorithm is applied to the frequency response functions obtained by using both sensors, leading to the estimation of the body mass value, as well as the three coordinates of the centre of mass and the six elements of the inertia tensor. An experimental example supports the use of the referred low-cost sensors.

Vibration of a Spring-Supported Body

1965 ◽  
Vol 7 (2) ◽  
pp. 185-192 ◽  
Author(s):  
P. Grootenhuis ◽  
D. J. Ewins
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Vertical Axis ◽  
The Body ◽  
Stiffness Ratio ◽  
Six Degrees Of Freedom ◽  
Centre Of Gravity ◽  
Longitudinal Stiffness ◽  
The Matrix

The equations of motion for a rigid body supported on four springs are derived for the general case of the centre-of-gravity being anywhere within the body and allowing for the sideways as well as the longitudinal stiffnesses of the springs. This constitutes a six-degrees-of-freedom case with three degrees of asymmetry. Coupling between motions in all directions occurs even when the centre-of-gravity is at the geometric centre with the exception then of vertical oscillations and rotation about the vertical axis. Any number of additional springs can be allowed for by adding terms to the expression for the potential energy stored in the springs. Allowance is made in the expression for kinetic energy for the products of inertia which arise with an offset centre-of-gravity. The real case is simulated for purposes of analysis by replacing the rigid body by a rectangular box with a light framework and all the mass concentrated at the eight corners. The matrix solution is changed into dimensionless parameters and the effect of an offset centre-of-gravity upon the eigenvalues and eigenvectors studied. Only the proportions of the box and the stiffness ratio between sideways to longitudinal stiffness of the springs remain as factors. The numerical example given is for proportions of height to width to length of 3/4/5 and for a stiffness ratio of 5. Small amounts of offset of the centre-of-gravity from the geometric centre do not alter the dynamic behaviour of the system much but displacing the total mass towards either a lower or an upper corner has marked effects. Some of the natural frequencies associated with motion in rotation when the system is symmetric become less than the frequencies connected with motion in translation for the centre-of-gravity being close to a corner connected to a spring. A large region free from any natural frequency arises when the centre-of-gravity is moved towards a corner furthest removed from the plane containing the springs. The asymptotic conditions for the position of the centre-of-gravity are also considered.

Gender determination of caucasoid hair using image analysis

1993 ◽  
Vol 51 ◽  
pp. 216-217
Author(s):  
T.B. Ball ◽  
W.M. Hess
Keyword(s):  
Image Analysis ◽  
Cross Sections ◽  
Scalp Hair ◽  
The Body ◽  
Equivalent Diameter ◽  
Cross Sectional ◽  
Hair Samples ◽  
Length Width ◽  
Morphological Differences

It has been demonstrated that cross sections of bundles of hair can be effectively studied using image analysis. These studies can help to elucidate morphological differences of hair from one region of the body to another. The purpose of the present investigation was to use image analysis to determine whether morphological differences could be demonstrated between male and female human Caucasian terminal scalp hair.Hair samples were taken from the back of the head from 18 caucasoid males and 13 caucasoid females (Figs. 1-2). Bundles of 50 hairs were processed for cross-sectional examination and then analyzed using Prism Image Analysis software on a Macintosh llci computer. Twenty morphological parameters of size and shape were evaluated for each hair cross-section. The size parameters evaluated were area, convex area, perimeter, convex perimeter, length, breadth, fiber length, width, equivalent diameter, and inscribed radius. The shape parameters considered were formfactor, roundness, convexity, solidity, compactness, aspect ratio, elongation, curl, and fractal dimension.

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