|
The simplest three-dimensional case of rotation is rotation of a body about a fixed axis of rotation: each point of the body moves in a plane perpendicular to the axis, carrying out a circular motion, with the circle centered at the intersection of the plane and the axis. Jump to: navigation, search Rotation of a planar figure around a point Rotation of a planar body is the movement when points of the body travel in circular trajectories around a fixed point called the center of rotation. ...
In physics, circular motion is movement with constant speed around in a circle: a circular path or a circular orbit. ...
The axis can be within the body, in which case the body is said to rotate upon itself, or spin, or outside it.
In the case of a rigid body the angle of rotation is a function of time which is the same for every point of the body.
An object may allow rotation with respect to an attached other object by means of one or more hinges (e.g. a door, scissors, a hinge joint). A hinge is a mechanical device that connects two solid objects, allowing rotation between them. ...
The front door of a house is often decorated to appear inviting. ...
Different types of scissors - sewing, kitchen, paper Scissors are a tool used for cutting thin material which requires little force. ...
This article is about a joint in zootomical anatomy. ...
Speed of rotation, angular acceleration, and torque
The speed of rotation is given by the angular frequency (rad/s) or frequency (turns/s, turns/min), or period (seconds, days, etc.). Angular frequency is a measure of how fast an object is rotating In physics (specifically mechanics and electrical engineering), angular frequency ω (also called angular speed) is a scalar measure of rotation rate. ...
Jump to: navigation, search Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...
Turn (geometry) The British Astronomer and Science writer Sir Fred Hoyle (1915 - 2001) in Astronomy (London 1962), proposed dividing the circle, or turn into 1000 milliturns. ...
Periodicity is the quality of occurring at regular intervals (e. ...
With one direction of rotation considered positive, the sign of the angular frequency indicates the direction of rotation.
The time-rate of change of angular frequency is the scalar version of angular acceleration (rad/s²). This change is caused by the scalar version of the torque, which can have a positive or negative value in accordance with the convention of positive and negative angular frequency. The ratio of torque and angular acceleration (how heavy is it to start, stop, or otherwise change rotation) is given by the moment of inertia. Angular acceleration is the rate of change of angular velocity over time. ...
The concept of torque in physics, also called moment or couple, originated with the work of Archimedes on levers. ...
Jump to: navigation, search Moment of inertia quantifies the rotational inertia of an object, i. ...
The energy required for / released during rotation is the torque times the rotation angle, the energy stored in a rotating object is one half of the moment of inertia times the square of the angular frequency. The power required for angular acceleration is the torque times the angular frequency. Jump to: navigation, search // Mechanical power In physics, power (symbol: P) is the amount of work W done per unit of time t. ...
Vectors According to the right-hand rule, moving away from the observer is associated with clockwise rotation and moving towards the observer with counterclockwise rotation, like most screws. In mathematics and physics, the right-hand rule is a convention for determining relative directions of certain vectors. ...
Jump to: navigation, search Screws come in a variety of shapes and sizes for different purposes. ...
The angular velocity vector also describes the direction of the axis of rotation. In the case of a fixed axis this direction is along that axis and the rotation process is described by a scalar, the angular frequency, as a function of time. Jump to: navigation, search Angular velocity describes the speed of rotation. ...
Similarly the torque vector also describes around which axis it tends to cause rotation, or in other words, the direction in which it tends to change the angular velocity vector. To maintain rotation around the fixed axis the total force has to be zero and the total torque vector has to be along the axis, so that it only changes the magnitude and not the direction of the angular velocity vector. In the case of a hinge, only the component of the torque vector along the axis has effect on the rotation, other forces and torques are compensated by the structure.
Centripetal force In the case of a spinning object, internal tensile stress provides the centripetal force that keeps the object together. Tensile stress (or tension) is the stress state leading to expansion; that is, the length of a material tends to increase in the tensile direction. ...
Jump to: navigation, search Centripetal force is the force pulling of an object toward the center of a circular path as the object goes around the circle. ...
A rigid body model neglects the accompanying strain. Jump to: navigation, search In physics, a rigid body is an idealisation of a solid body of finite size in which deformation is neglected. ...
If the body is not rigid this strain constitutes a change of shape. This is also expressed as changing shape due to the "centrifugal force". Jump to: navigation, search The term centrifugal force is used for two different, if sometimes easy to confuse, concepts. ...
Celestial bodies rotating about each other often have elliptic orbits. The special case of a circular orbits is an example of a rotation around a fixed axis: this axis is the line through the center of mass perpendicular to the plane of motion. The centripetal force is provided by gravity, see also two-body problem. This usually also applies for a spinning celestial body, so it need not be solid to keep together, unless the angular speed is too high in relation to its density. For example, for a celestial body of water one revolution has to take at least 3 hours and 18 minutes, regardless of size. If the density of the fluid is higher the time can be less. See orbital period. See also oblate for oblateness due to rotation, in particular of a fluid celestial body. Two bodies with similar mass orbiting around a common barycenter with elliptic orbits. ...
In astrodynamics or celestial mechanics a circular orbit is an elliptic orbit with the eccentricity equal to 0. ...
The center of mass or center of inertia of an object is a point at which the objects mass can be assumed, for many purposes, to be concentrated. ...
Jump to: navigation, search It has been suggested that Gravitational constant be merged into this article or section. ...
In mechanics, the two-body problem is a special case of the n-body problem that admits a closed form solution. ...
The orbital period is the time it takes a planet (or another object) to make one full orbit. ...
Oblate also refers to a member of the Roman Catholic religious order of the Missionary Oblates of Mary Immaculate, or in some cases to a lay or religious person who has officially associated himself (or herself) with a monastic community such as the Benedictines for reasons of personal enrichment without...
Constant angular speed The simplest case of rotation around a fixed axis is that of constant angular speed. There is no torque. The angle of rotation is a linear function of time, which modulo 360° is a periodic function.
An example of this is the two-body problem with circular orbits. In mechanics, the two-body problem is a special case of the n-body problem that admits a closed form solution. ...
In astrodynamics or celestial mechanics a circular orbit is an elliptic orbit with the eccentricity equal to 0. ...
See also |
Feeds |
Contact