Contact force
Encyclopedia
In physics
, a contact force is a force
that acts at the point of contact between two objects, in contrast to body forces. Contact forces are described by Newton's laws of motion
, as with all other forces in dynamics
.
Contact forces are ubiquitous and are responsible for most visible interactions between macroscopic collections of matter
. Pushing a car up a hill or kicking a ball are some of the everyday examples where contact forces are at work. In the first case the force is continuously applied by the person on the car, while in the second case the force is delivered in a short impulse. Certain contact forces describe specific phenomena and are important enough to have been given unique names. The most common instances of this include friction
, normal force
, and tension.
In the Standard Model
of modern physics, the four fundamental forces of nature
are known to be non-contact forces. The strong
and weak interaction
primarily deal with forces within atoms, while gravitational effects are only obvious on a macroscopic scale. Molecular and quantum physics show that the electromagnetic force is the fundamental interaction responsible for contact forces. The interaction between macroscopic objects can be roughly described as resulting from the electromagnetic interactions between protons and electrons of the atomic constituents of these objects. Everyday objects do not actually touch each other; rather contact forces are the result of the interactions of the electron
s at or near the surfaces of the objects (exchange force
).
Hence, we can see the many examples of contact forces in everyday life.
Contact forces can act through a rigid connector or a non rigid connector.
For example when a boy pulls a cart through a rope he is connecting the force applied through a non rigid connector (the rope).
He could also pull the cart through the handle of the cart hence transferring the force through the rigid connector (the handle).
But from case A the boy cannot push the cart (disadvantage of non rigid connector).
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
, a contact force is a force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
that acts at the point of contact between two objects, in contrast to body forces. Contact forces are described by Newton's laws of motion
Newton's laws of motion
Newton's laws of motion are three physical laws that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces...
, as with all other forces in dynamics
Dynamics
Dynamics may refer to:-Physics and engineering:* Dynamics , the time evolution of physical processes** Aerodynamics, the study of gases in motion...
.
Contact forces are ubiquitous and are responsible for most visible interactions between macroscopic collections of matter
Matter
Matter is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume...
. Pushing a car up a hill or kicking a ball are some of the everyday examples where contact forces are at work. In the first case the force is continuously applied by the person on the car, while in the second case the force is delivered in a short impulse. Certain contact forces describe specific phenomena and are important enough to have been given unique names. The most common instances of this include 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:...
, normal force
Normal force
In mechanics, the normal force F_n\ is the component, perpendicular to the surface of contact, of the contact force exerted on an object by, for example, the surface of a floor or wall, preventing the object from penetrating the surface.The normal force is one of the components of the ground...
, and tension.
In the Standard Model
Standard Model
The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...
of modern physics, the four fundamental forces of nature
Fundamental interaction
In particle physics, fundamental interactions are the ways that elementary particles interact with one another...
are known to be non-contact forces. The strong
Strong interaction
In particle physics, the strong interaction is one of the four fundamental interactions of nature, the others being electromagnetism, the weak interaction and gravitation. As with the other fundamental interactions, it is a non-contact force...
and weak interaction
Weak interaction
Weak interaction , is one of the four fundamental forces of nature, alongside the strong nuclear force, electromagnetism, and gravity. It is responsible for the radioactive decay of subatomic particles and initiates the process known as hydrogen fusion in stars...
primarily deal with forces within atoms, while gravitational effects are only obvious on a macroscopic scale. Molecular and quantum physics show that the electromagnetic force is the fundamental interaction responsible for contact forces. The interaction between macroscopic objects can be roughly described as resulting from the electromagnetic interactions between protons and electrons of the atomic constituents of these objects. Everyday objects do not actually touch each other; rather contact forces are the result of the interactions of the electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s at or near the surfaces of the objects (exchange force
Exchange force
In physics the term exchange force has been used to describe two distinct concepts which should not be confused.-Exchange of force carriers in particle physics:...
).
Example
An example of contact force commonly encountered in college-level physics is the force between two masses A and B which are lying next to each other and a force F is being applied on one of the masses, for example A. In such a case, the contact force will be proportional to the mass of B.Hence, we can see the many examples of contact forces in everyday life.
Contact forces can act through a rigid connector or a non rigid connector.
For example when a boy pulls a cart through a rope he is connecting the force applied through a non rigid connector (the rope).
He could also pull the cart through the handle of the cart hence transferring the force through the rigid connector (the handle).
But from case A the boy cannot push the cart (disadvantage of non rigid connector).