# Convert kilogram-force [kgf] <—> joule/meter [J/m]

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A kilogram-force (kgf), also called kilopond (kp), is a gravitational metric unit of force. It is equal to the force exerted by one kilogram of mass in a standard gravitational field. Therefore, one kilogram-force is by definition equal to 9.80665 N. A kilogram-force is a convenient unit because its value is equal to the weight of an object with a mass of 1 kg and it is easy to imagine what is, e.g., a 10 kgf force.A joule per meter (J/m) is a metric unit of force. In mechanics, a joule is defined as the work done by a force of one newton acting to move an object through a distance of one meter in the direction in which the force is applied (1 J = 1 N·m). Therefore, joule per meter is equal to newton.
1 kilogram-force [kgf] = 9.80664999999998 joule/meter [J/m]

# More about Force

Three forces, which are in dynamic equilibrium, are acting on this surfer: gravity, lift and drag

Overview

Equilibrium

Fundamental Forces in the Universe

Strong Force

Electromagnetic Force

Weak Force

Gravitational Force

Tides

Non-Fundamental Forces

Normal Force

Friction

Interesting Facts about Forces

## Overview

Physics defines force as an influence that changes the movement of a body, be it external movement or movement within the body, such as changing its shape. For example, when a stone is released, it falls down because it is pulled by the Earth’s force of gravity. During the impact it bends the blades of grass that it falls on — the force of the weight of the stone is making them move and change their shape.

Force is a vector, meaning that it has a direction. When several forces are acting on an object and pulling it in different directions, these forces may be in equilibrium, meaning that their vector sum is zero. In this case, the object would be at rest. The stone from the earlier example may roll after it hits the ground, but it will eventually stop. The force of gravity is still pulling it down, but at the same time the normal force, or ground reaction force, is pushing the stone up. The net sum of these forces is zero, they are in equilibrium, and the stone is not moving.

The SI unit of force is the newton. One newton corresponds to the net force that accelerates an object with mass of one kilogram by one meter per second squared.

## Equilibrium

One of the first scientists to investigate forces and to create a model of their interaction with matter in the universe was Aristotle. According to his model, if the net vector sum of the forces acting upon an object is zero, the forces are in the state of equilibrium and the object is stationary. This model was later corrected to include objects moving at a constant velocity when the forces are in equilibrium. This type of equilibrium is called dynamic equilibrium, while the one with the object at rest is called static equilibrium.

## Fundamental Forces in the Universe

Forces in nature cause objects to move or to stay in place. There are four fundamental forces in nature: strong, electromagnetic, weak, and gravitational. All the other forces are subsets of these four. Strong and weak forces, contrast to electrical and gravitational forces, affect matter on the nuclear level only. They do not work over large distances.

### Strong Force

Strong force is the strongest of the four forces. It acts upon the elements of the nucleus of the atom, keeping neutrons and protons together. This force is carried by gluons and binds quarks together to form larger particles. Quarks form neutrons, protons, and other larger particles. Gluons are smaller elementary particles, which have no substructure, and move between quarks as force carriers. The movement of gluons creates strong force between quarks. This is the force that makes up matter in the universe.

Pole-type transformers in Kyoto, Japan

### Electromagnetic Force

Electromagnetic force is the second strongest force. It is an interaction between particles with the opposite or the same electrical charges. When two particles have the same charge, that is, they are both positive, or both negative, they repel each other. If, on the other hand, they have the opposite charge, where one is positive and one is negative, they are attracted to each other. This movement of particles, which are repelled or attracted to other particles, is electricity — a physical phenomenon which we use in daily lives and in most of technology.

The electromagnetic force can account for chemical reactions, light, and electricity, as well as interactions between molecules, atoms, and electrons. These interactions between particles are responsible for the shapes that solid objects take in the world. The electromagnetic force prevents two solid objects from permeating each other, because the electrons in one object repel the electrons of the same charge of the other object. Historically electric and magnetic forces were treated as separate influences, but eventually it was discovered that they are related. Most objects have neutral charge, but it is possible to change the charge of an object by rubbing two objects together. The electrons will travel between the two materials, being attracted to the opposite charged electrons in the other material. This will leave more of the same charge electrons on the surface of each object, thus changing the dominant charge of the object overall. For example, if one rubs hair with a sweater, and then lifts the sweater away, the hair will stand up and “follow” the sweater. This is because electrons on the surface of the hair are attracted more to the atoms on the surface of the sweater than electrons on the surface of the sweater are attracted to the atoms on the surface of the hair. Hair or other similarly charged objects will also be attracted to the neutrally charged surfaces as well.

### Weak Force

Weak force is weaker than the electromagnetic one. Just like gluons carry the strong force, W and Z bosons carry the weak force. They are elementary particles that are emitted or absorbed. W bosons facilitate the process of radioactive decay, while the Z bosons do not affect the particles that they come in contact with, other than transferring momentum. Carbon dating, a process of determining the age of organic matter, is possible because of the weak force. It is used to establish the age of historical artifacts, and is based on evaluating the decay of carbon present in this organic matter.

Lake Ontario. Mississauga (Canada). Starry Night

### Gravitational Force

Gravitational force is the weakest of the four. It keeps the astronomical objects in their positions in the universe, is responsible for tides, and causes objects to fall on the ground when released. It is the force that acts upon objects, attracting them to each other. The strength of this attraction increases with the object’s mass. Like the other forces, it is believed to be mediated by particles, gravitons, but these particles have not been detected yet. Gravitation affects how astronomical objects move, and the motion can be calculated, based on the mass of the surrounding objects. This dependency allowed scientists to predict that Neptune exists by watching the motion of Uranus, before Neptune was seen in the telescope. This was because the movement of Uranus was inconsistent with its predicted motion, based on the astronomical objects known at the time, therefore scientists deducted that another planet, yet unseen, must be affecting its movement patterns.

According to the theory of relativity, gravity also changes the spacetime continuum, the four dimensional space that everything, including humans, exist in. According to this theory, the curvature of spacetime increases with mass, and because of that it is easier to notice with objects as large as planets or greater in mass. This curvature was proved experimentally, and can be seen when two synchronized clocks are compared, where one is stationary and one moves for a considerable distance along a body with large mass. For example, if the clock is moved around the orbit of the earth, as in Hafele–Keating experiment, then the time it shows will be behind the stationary clock, because the spacetime curvature causes the time to run slower for the clock in motion.

The force of gravity causes objects to accelerate when falling towards another object, and this is noticeable when the difference in mass between the two is great. This acceleration can be calculated based on the mass of the objects. For objects falling towards the Earth it is about 9.8 meters per second squared.

Sea rocks

### Tides

Tides are examples of gravitational force in action. They are caused by the gravitational forces of the Moon, the Sun, and the Earth. Contrast to solid objects, water can change shape easily when forces act upon it. Therefore when gravitational forces of the Moon and the Sun act upon the Earth, the ground surface does not get pulled by these forces as much as the water does. The Moon and the Sun move across the sky, and the water on Earth follows them, causing tides. The forces that act upon the water are called tidal forces; they are a variety of gravitational forces. The Moon, being closer to the Earth, has a stronger tidal force compared to the Sun. When the tidal forces of the Sun and the Moon act in the same direction, the tide is the strongest and is called spring tide. When these two forces are in opposition, the tide is the weakest and is called a neap tide.

Tides happen with different frequency depending on the geographical area. Because gravity of the Moon and the Sun pulls both the water and the entire planet Earth, in some areas tides occur both when the gravitational force pulls the water and the Earth in the same or in different directions. In this case the high and low tide pair happens twice in one day. In some areas this happens only once a day. Tide patterns on the coast depend on the shape of the coast, the deep ocean tide patterns, and the location of the Moon and the Sun, as well as the interaction of their gravitational forces. In some locations, the duration of time between tides can last up to several years. Depending on the coastline and the depth of the ocean, tides can cause currents, storms, changes in wind patterns, and fluctuation in air pressure. Some places use special clocks to calculate when the next tide will happen. They are configured based on the tidal occurrences in the area, and need to be reconfigured when moved to another location. In some areas tide clocks are not effective because tides cannot be predicted easily there.

The tidal force which moves water to and from the shore is sometimes used to generate power. Tidal mills have used this force for centuries. The basic construction has a water reservoir, and the water is let in at high tide and out at low tide. The kinetic energy of the flowing water moves the wheel of the mill, and the generated power is used to perform work, for example, grinding grains into flour. While there are a number of problems with this system, including dangers to the ecosystem where this mill is built, this method of generating energy has potential, because it is a renewable and a reliable source of power.

## Non-Fundamental Forces

The forces that are derivatives of the fundamental forces are called non-fundamental forces.

Equilibrium

### Normal Force

One of the non-fundamental forces is the normal force, which acts perpendicular to the surface of the object and pushes outward, resisting the pressure from other objects. When an object is placed on a surface, the magnitude of the normal force is equal to the net force pressing against the surface. On a flat surface, when forces other than gravity are in equilibrium, the normal force is equal to gravitational force in magnitude and opposite in direction. The vector sum of the two forces is then zero and the object is stationary or moving at a constant speed. When the object is on an incline and other forces are in equilibrium, the sum of gravitational and normal forces points downwards (but not directly down, perpendicular to the horizon), and the object slides down, along the incline.

Wider tires provide better friction

### Friction

Friction is a force parallel to the surface of an object and opposite its motion. It occurs when two objects are sliding against each other (kinetic friction), or when a stationary object is placed on an inclined surface (static friction). This force is employed when setting objects in motion, for example wheels grip to the ground due to friction. Without it they would not have been able to propel vehicles. The friction between the rubber of the tires and the ground is strong enough to ensure that the tires are not sliding along the ground and allows for the rolling movement and for better control of the direction of the motion. Friction of a rolling object, rolling friction or rolling resistance, is not as strong as the dry friction of two objects sliding against each other. Friction is used in stopping with the use of breaks — the wheels of a vehicle are slowed down by dry friction in the disk or drum brakes. In some cases friction is undesirable because it slows down motion and wears out mechanical components. Liquids or smooth surfaces are used to minimize friction.

## Interesting Facts about Forces

Forces can deform solid objects or change volume and pressure in liquids and gases. This happens when forces are applied unequally to different parts of the object or substance. In some cases when enough force is applied to a heavy object, it can be compressed into a very small sphere. If this sphere is small enough, smaller than a certain radius, then a black hole can be formed. This radius is called the Schwarzschild radius. It varies based on the mass of the object and can be calculated using a formula. This sphere’s volume is so small, that compared to the mass of the object, it is almost zero. Because the mass of black holes is so highly condensed, they have an extremely high gravitational pull, so that other objects cannot escape it, and neither can light. Black holes do not reflect any light, so they appear to be completely black. This is why they are called black holes. Scientists believe that large stars at the end of their life turn into black holes and can grow in mass by absorbing other objects that are within a given radius.

References

This article was written by Kateryna Yuri.

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## Definitions

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### Force

In physics, a force is any influence that causes an object to undergo a certain change, either concerning its movement, direction, or geometrical construction. It is measured with the SI unit of newtons. In other words, a force is that which can cause an object with mass to change its velocity, that is, to accelerate, or which can cause a flexible object to deform.

The SI unit of force is the newton (N), which is the force required to accelerate a one kilogram mass at a rate of one meter per second squared, or kg·m·s⁻². The corresponding CGS unit is the dyne, the force required to accelerate a one gram mass by one centimeter per second squared, or g·cm·s⁻².

Unit definitions

### Using the Force Converter

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You can use this online converter to convert between several hundred units (including metric, British and American) in 76 categories, or several thousand pairs including acceleration, area, electrical, energy, force, length, light, mass, mass flow, density, specific volume, power, pressure, stress, temperature, time, torque, velocity, viscosity, volume and capacity, volume flow, and more.
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In this calculator, E notation is used to represent numbers that are too small or too large. E notation is an alternative format of the scientific notation a · 10x. For example: 1,103,000 = 1.103 · 106 = 1.103E+6. Here E (from exponent) represents “· 10^”, that is “times ten raised to the power of”. E-notation is commonly used in calculators and by scientists, mathematicians and engineers.

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