## Normal force

Normal force is the force that the ground pushes back up with; If there was no normal force, you would slowly seep into the ground. The normal force on a object is always perpendicular at a right angle to the surface the object is on. On a flat s ...

## Oscillation

Something that oscillates is something that "vibrates", or repeats the same pattern. Many things in nature move back-and-forth or up-and down when pushed or struck. In time, natural oscillators slow down and stop because of friction.

## Physical compression

Physical compression means that a material under compressive stress reduces its volume. There are different uses of compression in physics and engineering. By compression it is possible to measure mechanical properties of materials such as compre ...

## Pitch, yaw, and roll

Pitch, yaw and roll are the three dimensions of movement when an object moves through a medium. The terms may be used to describe an aeroplanes movements through the air. They are also applied to fish moving through water, and spacecraft moving t ...

## Pneumatics

Pneumatics is the use of compressed air for mechanical motion. It has many uses. Pneumatic transfer systems are employed in many industries to move powders and devices. Pneumatic devices are also used where electric motors cannot be used for safe ...

## Polar moment of inertia

Note: Different disciplines use the term moment of inertia to refer to different moments. In physics, moment of inertia is strictly the second moment of mass with respect to distance from an axis, which characterizes an objects angular accelerati ...

## Principle of stationary action

Pierre Maupertuis stated in 1746 that many processes in nature are either optimal, or they take extreme values. This is known as the principle of stationary action and is a part of mechanics. It states that physical fields and particles will some ...

## Quantum entanglement

Quantum entanglement is the name given to a special connection between pairs or groups of quantum systems, or any objects described by quantum mechanics. Quantum entanglement is one of the biggest parts of quantum mechanics that makes it hard to ...

## Quantum mechanics

Quantum mechanics explains how the universe works at a scale smaller than atoms. It is also called quantum physics or quantum theory. Mechanics is the part of physics that explains how things move and quantum is the Latin word for how much. A qua ...

## Rotation

Rotation is the movement of an object in a circular motion. A two-dimensional object rotates around a center or point of rotation. A three-dimensional object rotates around a line called an axis. If the axis of rotation is within the body, the bo ...

## Rube Goldberg machine

A Rube Goldberg machine is a machine that looks complicated but has a very simple function, such as ironing a shirt. It is an expression used to identify something that does very simple tasks in a very complex way. The expression was named after ...

## Schrodinger equation

The Schrodinger equation is a differential equation that forms the basis of quantum mechanics, one of the most accurate theories of how subatomic particles behave. It is a mathematical equation that was thought of by Erwin Schrodinger in 1925. It ...

## Seismic wave

Seismic waves are vibrating movement of the ground. Seismic waves can be caused by underground explosions, volcanic eruptions and man-made explosions that can vibrate the ground. Seismic waves go through the Earth’s layers. The speed of seismic w ...

## Statistical mechanics

Statistical mechanics is the application of probability theory, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force. ...

## Stress analysis

Stress analysis is the study of stresses and strains in materials and structures as force is applied against them. It is a topic in engineering. Stress may cause deformation or fractures in materials. Stress analysis is about finding out how much ...

## Surface wave

In physics, a surface wave can refer to a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gr ...

## Torsion (mechanics)

In solid mechanics, torsion is the twisting of an object that is result of an applied torque. In circular sections, the resultant shearing stress is perpendicular to the radius. The shear stress at a point on a shaft is: τ θ z = T r J {\displayst ...

## Two-body problem

The two-body problem is a problem from classical mechanics: there are two bodies which influence each other. Very often they attract or repel each other. In many cases they rotate. The problem uses bodies which are circles, or spheres. Solving th ...

## Work (physics)

In physics, a force does work when it acts on a body and there is a displacement of the point of application in the direction of the force. The work done by a force acting on a body is the force along the direction of the displacement multiplied ...

## Thermodynamics

Thermodynamics is a branch of physics that studies the movement of heat between different objects. Thermodynamics also studies the change in pressure and volume of objects. A branch of math called statistics is often used in thermodynamics to loo ...

## Absolute zero

Absolute zero is the temperature at which the particles of matter are at their lowest energy points. Some people think that at absolute zero particles lose all energy and stop moving. This is not correct. In quantum physics there is something cal ...

An adiabatic process is a thermodynamic process where a fluid becomes warmer or cooler without getting heat from, or giving it to, something else. Usually the temperature instead changes because of changes in pressure. Adiabatic cooling is the us ...

Blackbody radiation is radiation produced by heated objects, particularly from a blackbody. A blackbody is an object that absorbs all radiation that falls on it. This also means that it will also radiate at all frequencies that heat energy produc ...

## Boiling point

The boiling point of a substance is the temperature at which the substance boils, or enters a state of rapid evaporation. For pure water this is 100° Celsius or 212° Fahrenheit. This is measured at one atmosphere, that is, the air pressure at sea ...

## Conservation of energy

This article refers to the law of conservation of energy in physics. For energy resources sustainably, see: Energy conservation. In physics, the conservation of energy is that energy can not be created or destroyed, it can only be changed from on ...

## Diffusion

Diffusion is a process where molecules of a material move from an area of high concentration to an area of low concentration until it has reached equilibrium. Diffusion usually happens in a solution in gas, a liquid and occasionally colloids. It ...

## Enthalpy

Enthalpy is a concept used in science and engineering when heat and work need to be calculated. The name comes from the Greek word "enthalpos", meaning "to put heat into". The idea and the word were made up by the Dutch scientist Heike Kamerlingh ...

## Entropy

The entropy of an object is a measure of the amount of energy which is unavailable to do work. Entropy is also a measure of the number of possible arrangements the atoms in a system can have. In this sense, entropy is a measure of uncertainty or ...

## Exothermic reaction

An exothermic reaction is a chemical reaction where the substances reacting release energy as heat. An example of this is combustion. Exothermic reactions transfer energy to the surroundings. The reaction that does the complete opposite is an end ...

## Exothermic reactions

An exothermic reaction is a reaction where the substances react chemically to release energy in the form of heat. An example of this is combustion burning. Exothermic reactions transfer energy to the surroundings. The energy is usually transferre ...

## First law of thermodynamics

The first law of thermodynamics states that energy can neither be created nor destroyed; it can changed only from one form to another. The law forms the basis of the principle of conservation of energy. This means that anything that uses energy i ...

## Flammability

Flammability or inflammability means that something can be set on fire easily. It will burn easily. The words come from Latin. The word at the base is in-flammare. It means something like "to put fire to a thing". Inflammable and flammable are us ...

## Fugacity

In thermodynamics, the fugacity is a state function of any isothermal system. The fugacity, which has units of pressure, represents the tendency of a fluid to escape or expand isothermally. For gases at low pressures where the ideal gas law holds ...

## Glass transition

The glass transition is the transition of amorphous solids from a hard and brittle state into a molten or rubber-like state. An amorphous solid that goes through a glass transition is called a glass. Supercooling a viscous liquid into the glass s ...

## Heat

Heat is the sum of the kinetic energy of atoms or molecules. In thermodynamics, heat means energy which is moved between two things, when one of them has a higher temperature than the other thing. Adding heat to something increases its temperatur ...

## Heat engine

In engineering and thermodynamics, a heat engine converts heat energy to mechanical work by using the temperature difference between a hot "source" and a cold "sink". Heat is transferred from the source, through the "working body" of the engine, ...

## Ideal gas law

The ideal gas law is the equation of a possible ideal gas, first made by Benoit Paul Emile Clapeyron in 1834. The state or amount of an amount of gas is found by using its pressure, volume, and temperature in the equation: p V = n R T {\displayst ...

## Joules laws

Joules laws are two: first about heat produced by an electric current, and second about how the energy of a gas relates to pressure, volume. Joules first law shows the relation between heat generated by an electric current flowing through a condu ...

## Kinetic theory

Kinetic theory or kinetic theory of gases attempts to explain overall properties of gases, such as pressure, temperature, or volume, by considering their molecular composition and motion. The theory basically states that pressure is not caused by ...

## Laws of thermodynamics

There are four laws of thermodynamics. They talk about temperature, heat, work, and entropy. They are used in thermodynamics and other sciences, for example chemistry. Thermodynamics had three main laws: the first law, the second law, and the thi ...

## The Mpemba effect

The Mpemba effect is that hot water can, under certain circumstances, not only freeze but do so quicker than colder water. This phenomenon has been reported as working as far back as Ancient Greece, even though it would seem contradictory to the ...

## Negative temperature

In physics, absolute zero is the coldest temperature. At that point, subatomic particles stop moving. Certain things can reach temperatures below absolute zero, known as negative temperatures. This is very difficult to do, and only very small obj ...

## Negentropy

Negentropy is reverse entropy. It means things becoming more in order. By order is meant organisation, structure and function: the opposite of randomness or chaos. One example of negentropy is a star system such as the Solar System. Another examp ...

## Raoults law

Raoults law states that the vapour pressure of a binary solution containing a non-volatile solute is directly related to the mole fraction of solvent in the solution. Also, it states that the vapour pressure of each component in a binary solution ...

## Second law of thermodynamics

The second law of thermodynamics says that when energy changes from one form to another form, or matter moves freely, entropy in a closed system increases. Differences in temperature, pressure, and density tend to even out horizontally after a wh ...

## Surface energy

There is an attraction between molecules in liquids and this is why a liquid stays together. The intermolecular distance in liquid is such that it is attracted to all the surrounding molecules. This attraction causes negative potential energy for ...

## Temperature

Temperature is how hot or cold something is. Our bodies can feel the difference between something which is hot and something which is cold. To measure temperature more accurately, a thermometer can be used. Thermometers use a temperature scale to ...

## Thermal expansion

In physics, thermal expansion is the likelihood of matter to change in volume in response to a change in temperature. When a substance is heated, its basic particles move around more quickly and by doing so generally maintain a greater average se ...

## Thermal physics

Thermal physics is the combined study of thermodynamics, statistical mechanics, and kinetic theory. This umbrella-subject is typically designed for physics students and functions to provide a general introduction to each of three core heat-relate ...