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Force  

Common symbols

F, F 
SI unit  newton 
In SI base units  1 kg·m/s^{2} 
Derivations from
other quantities 
F = m a 
In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, 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. Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F.
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. If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object
Related concepts 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 an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the socalled internal mechanical stress. Such internal mechanical stresses cause no accelation of that body as the forces balance one another. 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. Stress usually causes deformation of solid materials, or flow in fluids.
Property/Interaction  Gravitation  Weak  Electromagnetic  Strong  

(Electroweak)  Fundamental  Residual  
Acts on:  Mass  Energy  Flavor  Electric charge  Color charge  Atomic nuclei 
Particles experiencing:  All  Quarks, leptons  Electrically charged  Quarks, Gluons  Hadrons 
Particles mediating:  Graviton (not yet observed) 
W^{+} W^{−} Z^{0}  γ  Gluons  Mesons 
Strength in the scale of quarks:  10^{−41}  10^{−4}  1  60  Not applicable to quarks 
Strength in the scale of protons/neutrons: 
10^{−36}  10^{−7}  1  Not applicable to hadrons 
20 
newton (SI unit) 
dyne 
kilogramforce, kilopond 
poundforce  poundal  

1 N  ≡ 1 kg⋅m/s^{2}  = 10^{5} dyn  ≈ 0.10197 kp  ≈ 0.22481 lbf  ≈ 7.2330 pdl 
1 dyn  = 10^{−5} N  ≡ 1 g⋅cm/s^{2}  ≈ 1.0197 × 10^{−6} kp  ≈ 2.2481 × 10^{−6} lbf  ≈ 7.2330 × 10^{−5} pdl 
1 kp  = 9.80665 N  = 980665 dyn  ≡ g_{n}⋅(1 kg)  ≈ 2.2046 lbf  ≈ 70.932 pdl 
1 lbf  ≈ 4.448222 N  ≈ 444822 dyn  ≈ 0.45359 kp  ≡ g_{n}⋅(1 lb)  ≈ 32.174 pdl 
1 pdl  ≈ 0.138255 N  ≈ 13825 dyn  ≈ 0.014098 kp  ≈ 0.031081 lbf  ≡ 1 lb⋅ft/s^{2} 
The value of g_{n} as used in the official definition of the kilogramforce is used here for all gravitational units. 
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