# Force

**forcesattractiveforce vectorelastic forceforcingloadresistance forcedriving forceforce energyimplying**

In physics, a force is any interaction that, when unopposed, will change the motion of an object.wikipedia

1,116 Related Articles

### Physics

**physicistphysicalphysicists**

In physics, a force is any interaction that, when unopposed, will change the motion of an object.

Physics (from, from φύσις phýsis "nature") is the natural science that studies matter and its motion and behavior through space and time and that studies the related entities of energy and force.

### Mass

**inertial massgravitational massweight**

A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate.

The object's mass also determines the strength of its gravitational attraction to other bodies.

### Torque

**momentmoment armtorques**

Concepts related to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object.

Torque, moment, or moment of force is the rotational equivalent of linear force.

### Motion (physics)

**motionmovementlocomotion**

In physics, a force is any interaction that, when unopposed, will change the motion of an object.

An object's motion cannot change unless it is acted upon by a force, as described.

### Pressure

**water pressurenegative pressurefluid pressure**

Pressure, the distribution of many small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate.

Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.

### Thrust

**thrustingexcess thrustlbf**

Concepts related to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object.

Thrust is a reaction force described quantitatively by Newton's third law.

### Drag (physics)

**dragaerodynamic dragair resistance**

Concepts related to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object.

In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid.

### Newton (unit)

**kNnewtonN**

It is measured in the SI unit of newtons and represented by the symbol F.

The newton (symbol: N) is the International System of Units (SI) derived unit of force.

### Acceleration

**decelerationacceleratem/s 2**

A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate.

An object's acceleration is the net result of all forces acting on the object, as described by Newton's Second Law.

### Simple machine

**simple machinescompound machinecompound machines**

Philosophers in antiquity used the concept of force in the study of stationary and moving objects and simple machines, but thinkers such as Aristotle and Archimedes retained fundamental errors in understanding force.

A simple machine is a mechanical device that changes the direction or magnitude of a force.

### Statics

**statichydrostatic forcestability problems**

Philosophers in antiquity used the concept of force in the study of stationary and moving objects and simple machines, but thinkers such as Aristotle and Archimedes retained fundamental errors in understanding force.

Statics is the branch of mechanics that is concerned with the analysis of loads (force and torque, or "moment") acting on physical systems that do not experience an acceleration (a=0), but rather, are in static equilibrium with their environment.

### Dynamics (mechanics)

**dynamicsdynamickinetics**

Philosophers in antiquity used the concept of force in the study of stationary and moving objects and simple machines, but thinkers such as Aristotle and Archimedes retained fundamental errors in understanding force.

Dynamics is the branch of classical mechanics concerned with the study of forces and their effects on motion.

### Inertia

**inertialinertia forceinertial forces**

By the early 20th century, Einstein developed a theory of relativity that correctly predicted the action of forces on objects with increasing momenta near the speed of light, and also provided insight into the forces produced by gravitation and inertia.

The principle of inertia is one of the fundamental principles in classical physics that are still used today to describe the motion of objects and how they are affected by the applied forces on them.

### Mechanical advantage

**leveragedrive ratioideal mechanical advantage**

The mechanical advantage given by a simple machine allowed for less force to be used in exchange for that force acting over a greater distance for the same amount of work.

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system.

### Projectile

**projectileskinetic kill vehiclekinetic projectile**

This theory, based on the everyday experience of how objects move, such as the constant application of a force needed to keep a cart moving, had conceptual trouble accounting for the behavior of projectiles, such as the flight of arrows.

A projectile is any object thrown into space (empty or not) by the exertion of a force.

### Deformation (engineering)

**deformationplastic deformationdeformed**

Stress usually causes deformation of solid materials, or flow in fluids.

an applied force (the deformation energy in this case is transferred through work) or

### Newton's laws of motion

**laws of motionNewton's second lawNewton's second law of motion**

A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time.

They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces.

### Time derivative

**rate of changeExample: circular motiontime rate of change**

The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time.

force is the time derivative of momentum

### Energy

**energiesenergy transfertotal energy**

In the special theory of relativity, mass and energy are equivalent (as can be seen by calculating the work required to accelerate an object).

The SI unit of energy is the joule, which is the energy transferred to an object by the work of moving it a distance of 1 metre against a force of 1 newton.

### Reaction (physics)

**reactionreaction forceaction and reaction**

This law is sometimes referred to as the action-reaction law, with called the action and the reaction.

As described by the third of Newton's laws of motion of classical mechanics, all forces occur in pairs such that if one object exerts a force on another object, then the second object exerts an equal and opposite reaction force on the first.

### Equivalence principle

**strong equivalence principleequivalentPrinciple of Equivalence**

Since there is no experiment that can distinguish whether it is the vehicle that is at rest or the outside world that is at rest, the two situations are considered to be physically indistinguishable.

By contrast, in Newtonian mechanics, gravity is assumed to be a force.

### General relativity

**general theory of relativityrelativitygeneral relativity theory**

However, while kinematics are well-described through reference frame analysis in advanced physics, there are still deep questions that remain as to what is the proper definition of mass. General relativity offers an equivalence between space-time and mass, but lacking a coherent theory of quantum gravity, it is unclear as to how or whether this connection is relevant on microscales.

Such deviations are caused by external forces acting on a body in accordance with Newton's second law of motion, which states that the net force acting on a body is equal to that body's (inertial) mass multiplied by its acceleration.

### Four-force

This relation is correct in relativity when F^\mu is the four-force, m is the invariant mass, and A^\mu is the four-acceleration.

In the special theory of relativity, four-force is a four-vector that replaces the classical force.

### Euclidean vector

**vectorvectorsvector addition**

A force has both magnitude and direction, making it a vector quantity.

Vectors play an important role in physics: the velocity and acceleration of a moving object and the forces acting on it can all be described with vectors.

### Closed system

**closedclosed systemsclosed-cycle**

More generally, in a closed system of particles, all internal forces are balanced.

In nonrelativistic classical mechanics, a closed system is a physical system that doesn't exchange any matter with its surroundings, and isn't subject to any net force whose source is external to the system.