Rolling
Encyclopedia
Rolling is a combination of rotation
(of a radially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that the two are in contact with each other without sliding. This is achieved by a rotational speed at the cylinder or circle of contact which is equal to the translational speed. Rolling of a round object typically requires less energy than sliding, therefore such an object will more easily move, if it experiences a force with a component along the surface, for instance gravity on a tilted surface; wind; pushing; pulling; an engine. Objects with corners, such as dice
, roll by successive rotations about the edge or corner which is in contact with the surface.
One of the most practical applications of rolling objects is the use of ball bearings in rotating devices. Made of a smooth metal substance, the spherical bearings are usually encased between two rings that can rotate independently of each other. In most mechanisms, the inner ring is attached to a stationary shaft (or axle). Thus, while the inner ring is stationary, the outer ring is free to move with very little friction
. This is the basis for which almost all motors
(such as those found in ceiling fans, cars, drills, etc.) rely on to operate. The amount of friction on the mechanism's parts depends on the quality of the ball bearings and how much lubrication is in the mechanism.
Rolling objects are also frequently used as tools for transportation. One of the most basic ways is by placing a (usually flat) object on a series of lined-up rollers, or wheel
s. The object on the wheels can be moved along them in a straight line, as long as the wheels are continuously replaced in the front (see history of bearings). This method of primitive transportation is efficient when no other machinery is available. Today, the most practical application of objects on wheels are cars
, trains, and other human transportation vehicles.
It is a misconception that rolling motion is only possible with round object, it is also possible in non round object. It is the motion in which body's point of contact is at rest with respect to supporting surface. In rolling sliding friction never acts.Rolling is perfect mixture of pure rotation and pure translation in round objects.In rolling object speed of partcle is higher as much as far away from point of contact with supporting surface.
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...
(of a radially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that the two are in contact with each other without sliding. This is achieved by a rotational speed at the cylinder or circle of contact which is equal to the translational speed. Rolling of a round object typically requires less energy than sliding, therefore such an object will more easily move, if it experiences a force with a component along the surface, for instance gravity on a tilted surface; wind; pushing; pulling; an engine. Objects with corners, such as dice
Dice
A die is a small throwable object with multiple resting positions, used for generating random numbers...
, roll by successive rotations about the edge or corner which is in contact with the surface.
One of the most practical applications of rolling objects is the use of ball bearings in rotating devices. Made of a smooth metal substance, the spherical bearings are usually encased between two rings that can rotate independently of each other. In most mechanisms, the inner ring is attached to a stationary shaft (or axle). Thus, while the inner ring is stationary, the outer ring is free to move with very little friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
. This is the basis for which almost all motors
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
(such as those found in ceiling fans, cars, drills, etc.) rely on to operate. The amount of friction on the mechanism's parts depends on the quality of the ball bearings and how much lubrication is in the mechanism.
Rolling objects are also frequently used as tools for transportation. One of the most basic ways is by placing a (usually flat) object on a series of lined-up rollers, or wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...
s. The object on the wheels can be moved along them in a straight line, as long as the wheels are continuously replaced in the front (see history of bearings). This method of primitive transportation is efficient when no other machinery is available. Today, the most practical application of objects on wheels are cars
CARS
Cars, or automobiles, motor cars, are wheeled motor vehicles used for transporting passengers.Cars or CARS may also refer to:-Entertainment:* Cars , a Disney/Pixar film series...
, trains, and other human transportation vehicles.
It is a misconception that rolling motion is only possible with round object, it is also possible in non round object. It is the motion in which body's point of contact is at rest with respect to supporting surface. In rolling sliding friction never acts.Rolling is perfect mixture of pure rotation and pure translation in round objects.In rolling object speed of partcle is higher as much as far away from point of contact with supporting surface.
See also
- Contact mechanicsContact mechanicsContact mechanics is the study of the deformation of solids that touch each other at one or more points. The physical and mathematical formulation of the subject is built upon the mechanics of materials and continuum mechanics and focuses on computations involving elastic, viscoelastic, and plastic...
- Rolling friction
- Frictional contact mechanics: Rolling contact
- Terrestrial locomotion in animals: Rolling
- Tumbling (gymnastics)Tumbling (gymnastics)In gymnastics, tumbling, also known as power tumbling is an acrobatic sporting discipline which combines some of the skills of artistic gymnastics on the floor with those of trampolining. It is practised on a 25 metre long spring track...