A physical
model is a smaller or larger physical copy of an object. The object being modelled may be small (for example, an atom) or large (for example, the
Solar SystemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
).
The geometry of the model and the object it represents are often
similarTwo geometrical objects are called similar if they both have the same shape. More precisely, one is congruent to the result of a uniform scaling of the other. Corresponding sides of similar polygons are in proportion, and corresponding angles of similar polygons have the same measure...
in the sense that one is a rescaling of the other; in such cases the scale is an important characteristic. However, in many cases the similarity is only approximate or even intentionally distorted.
A physical
model is a smaller or larger physical copy of an object. The object being modelled may be small (for example, an atom) or large (for example, the
Solar SystemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
).
The geometry of the model and the object it represents are often
similarTwo geometrical objects are called similar if they both have the same shape. More precisely, one is congruent to the result of a uniform scaling of the other. Corresponding sides of similar polygons are in proportion, and corresponding angles of similar polygons have the same measure...
in the sense that one is a rescaling of the other; in such cases the scale is an important characteristic. However, in many cases the similarity is only approximate or even intentionally distorted. Sometimes the
distortionA distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted...
is systematic with e.g. a fixed scale horizontally and a larger fixed scale vertically when modelling
topographyTopography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
of a large area (as opposed to a model of a smaller mountain region, which may well use the same scale horizontally and vertically, and show the true
slopeIn mathematics, the slope or gradient of a line describes its steepness, incline, or grade. A higher slope value indicates a steeper incline....
s).
Physical models allow visualization, from examining the model, of information about the thing the model represents. A model can be a physical object such as an architectural model of a building. Uses of an architectural model include visualization of internal relationships within the structure or external relationships of the structure to the environment. Other uses of models in this sense are as
toyA toy is an object used in play. Toys are usually associated with children and pets, but it is not unusual for adult humans and some non-domesticated animals to play with toys. Many items are manufactured to serve as toys, but goods, or services produced for other purposes can also be used as toys...
s.
Instrumented physical models are the most effective way of investigating fluid flows such as around
hydraulic structuresHydraulic engineering is a sub-discipline of civil engineering concerned with the flow and conveyance of fluids, principally water. This area of engineering is intimately related to the design of bridges, dams, channels, canals, levees, elevators, and to both sanitary and environmental...
. These models are scaled in terms of both geometry and important forces, for example using
Froude numberThe Froude number is a dimensionless number comparing inertia and gravitational forces. It may be used to quantify the resistance of an object moving through water, and compare objects of different sizes...
or
Reynolds numberIn fluid mechanics, the Reynolds number is a dimensionless number that gives a measure of the ratio of inertial forces to viscous forces and consequently quantifies the relative importance of these two types of forces for given flow conditions...
scaling (see
SimilitudeSimilitude is a concept used in the testing of engineering models. A model is said to have similitude with the real application if the two share geometric similarity, kinematic similarity and dynamic similarity...
).
A physical model of something large is usually smaller, and of something very small is larger. A physical model of something that can move, like a
vehicleA vehicle is a mechanical means of conveyance, a carriage or transport. Most often they are manufactured , although some other means of transport which are not made by humans also may be called vehicles; examples include icebergs and floating tree trunks.Vehicles may be propelled or pulled by...
or
machineA machine is any device that uses energy to perform some activity. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work. A simple machine is a device that transforms the direction or magnitude of a force without consuming any energy...
, may be completely static, or have parts that can be moved manually, or be powered. A physical model may show inner parts that are normally not visible. The purpose of a physical model on a smaller scale may be to have a better overview, for testing purposes, as
hobbyA hobby is an activity or interest that is undertaken for pleasure or relaxation in one's spare time.- Etymology :A hobby horse is a wooden or wickerwork toy made to be ridden just like a real horse...
or
toyA toy is an object used in play. Toys are usually associated with children and pets, but it is not unusual for adult humans and some non-domesticated animals to play with toys. Many items are manufactured to serve as toys, but goods, or services produced for other purposes can also be used as toys...
. The purpose of a physical model on a larger scale may be to see the structure of things that are normally too small to see properly or to see at all, for example a model of an
insectInsects are arthropods, having a hard exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae. They are the most diverse group of animals on the planet and include more than a million species that are already described. Insects represent more than half of all...
or of a
moleculeA molecule is defined as an electrically neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds. Molecules are distinguished from polyatomic ions in this strict sense...
.
A physical model of an
animalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
shows the animals physical composition without it walking or flying away, and without danger, and if the real animal is not available. A soft model of an animal is popular among children and some adults as cuddly toy.
A model of a
personA person is a legal concept both permitting rights to and imposing duties on one by law. In the fields of law, philosophy, medicine, and others, the term has specialised context-specific meanings....
may e.g. be a
dollA doll is an object that represents a baby or other human being. Dolls have been around since the dawn of human civilization, and have been fashioned from a vast array of materials, ranging from stone, clay, wood, bone, cloth and paper, to porcelain, china, rubber and plastic.While dolls have...
, a
statueA statue is a sculpture in the round representing a person or persons, an animal, or an event, normally full-length, as opposed to a bust, and at least close to life-size, or larger...
, and in fiction a
robotA robot is a virtual or mechanical artificial agent. In practice, it is usually an electro-mechanical machine which is guided by computer or electronic programming, and is thus able to do tasks on its own...
ic
humanoidA humanoid is a hybrid term from Latin humanus "human" and the Greek -oeides expressing likeness. The term was coined in the year of 1918 to refer to fossils considered close to human but not strictly human, including species now classified as Homo such as the Neanderthals.The term more generally...
, e.g. the mechas in the movie
A.I..
A model is a
3DThree-dimensional space is a geometric model of the physical universe in which we live. The three dimensions are commonly called length, width, and depth , although any three mutually perpendicular directions can serve as the three dimensions....
alternative for a 2D representation such as a
drawingDrawing is a visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Common instruments include graphite pencils, pen and ink, inked brushes, wax color pencils, crayons, charcoals, chalk, pastels, markers, stylus, or various metals like silverpoint...
or
photographA photograph is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a CCD or a CMOS chip. Most photographs are created using a camera, which uses a lens to focus the scene's visible wavelengths of light into a reproduction of...
, or in the case of a
globeA globe is a three-dimensional scale model of Earth or other spheroid celestial body such as a planet, star, or moon...
, a 3D, undistorted alternative for a flat world
mapA map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....
.
Physical models
- Model airplane
- Model car
A model car is a miniature representation, or scale model, of an automobile or similar powered vehicle, generally reproducing the shapes of actually-produced vehicles. Other miniature ground-running vehicles, such as trucks, buses, etc. are usually included in the general category of model cars...
- Model railway
- Model rocket
A model rocket is a small rocket capable of being launched by anybody, to generally low altitudes and recovered by a variety of means....