SI unit of Force is in Newtons (N). 1 Newton is equal to 1 kg*m*s^-2. The basic formula for force is F=ma where F stands for force, m stands for mass in kilograms and a stands for acceleration in m*s^-2. This is the Newton's second law of motion.
Atkinds, Peter. Physical Chemistry. 9th. Oxford University Press, 2009. Print.
The Newton is the SI unit of force. Strictly defined: the force that will give a mass of 1 kilogram an acceleration of 1 meter per second per second. It is not in everyday use. When did you last read a recipe that required you to add one newton of flour to a cake mixture? There is no logical reason for not doing so. A force of 1 Newton on the balance pan is approximately the force exerted downwards by 100 grams of flour on the pan.
So why not use kilograms per square metre also for the stress strain diagram? The pompous answer is that using Newtons allows this diagram to be used on a distant planet with a different mass. Weight is the expression of the force exerted by the earth on the mass of an object. The mass is the fundamental quantity, the weight, even on earth, varies with the position of the object. On the moon, 100 grams of flour would make a very big cake, if you measured it with a spring balance. 1 Newton of flour would work just like on earth.
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A force is a push, pull, or dragging on an object that changes its velocity or direction. A unit of force is an arbitrary measurement that we designate as "1" (unit), so that all other measurements of force are multiples of that unit.
Most often, force is designated as a newton (N) in the metric or SI system of measurement. The newton has applications in various scientific measurements. There are other units, not used as often.
Questions you may have include:
- What is the definition of the newton?
- What are some applications of the newton?
- what are other units of force?
This lesson will answer those questions. Useful tool: Units Conversion
Definition of newton
A newton is the force required to give a mass of 1 kilogram (1 kg) an acceleration of 1 meter per second per second (1 m/s2). It is abbreviated as N.
This unit of measurement is in the metric or SI system and is used in scientific work more than other units of force.
1 N is equivalent to 1 kg-m/s2.
Applications of the newton
The newton combined with other measurements is used in various applications.
Moment of force
The unit of torque or moment of force is the newton-meter (N-m), where m is the moment arm.
Energy, work and heat
The newton-meter (N-m) is also the definition of the joule (J), which is a unit of energy. It can be seen that the units of kinetic energy E = ½mv2 are in kilogram-meter2/seconds2 and kg-m2/s2 = N-m.
Power and radiant flux
Power is energy per second or N-m/s, with the unit of watt. This is also the unit for radiant flux or power from electromagnetic radiation.
Pressure
The unit of pressure is the pascal (P), which is the force per unit area (N-m2).
Other units of force
There are other units of force, not as commonly used as the newton.
Dyne
A dyne is the force required to give a mass of 1 gram (1 g) an acceleration of 1 centimeter per second per second (1 cm/s2). 1 N = 100,000 dynes.
You might use the dyne, if working with small objects.
Poundal and pound
A poundal is the force required to give a mass of 1 pound (1 lb) an acceleration of 1 foot per second per second (1 ft/s2). 1 poundal equals 0.1382 newtons.
A pound is the force applied on a mass of 1 pound (1 lb) by the acceleration due to gravity. It is a non-technical unit of force and is also called the weight.
These units of force are in the English system and are seldom used in scientific measurements.
Summary
A force acts on an object to change its velocity or direction. In most scientific work, force is designated as a newton (N) in the metric or SI system of measurement. The newton has applications in various scientific measurements. There are other units, not used as often.
Be forceful in your actions
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As per the second law of motion proposed by Newton, force is defined or expressed as the product of mass and acceleration.
In both the SI system (the International System of Units) and in the MKS system, the unit of mass is kilogram, abbreviated as kg, and the unit of acceleration is m/s². Therefore, the unit of force is kg m/s², which is what we refer to as Newton or N.
In the CGS system of units, the unit of mass is gram or g, and the unit of acceleration is cm/s². Therefore, the CGS unit of force is g cm/s², which is called dyne or Dyn.
In the FPS system of units, the unit of mass is pound or lb, and the unit of acceleration is feet per second squared or ft/s². Therefore, the FPS unit of force is lb-ft/s², which is called poundal or pdl.
Derivation of SI Unit of Force:
From Newton’s Second Law of motion, force is equal to the rate of change in momentum (P). We also know that momentum (P) is the product of mass(m) and velocity(v) .
Force = Rate of change of momentum
= P/ t {where P stands for momentum and t for time}
= mv/ t { P= mv}
Force= mass*velocity / time -- (replacing terms with their respective units)
Newton = (kg*m)/sec⁻²
Where,
Unit of Force = Newton
Unit of mass = Kilogram
Unit of time = Second
Unit of velocity = Metre / Second
NOTE: Displacement is the shortest distance from the initial to the final point. Inshort,displacement is distance in vector form(same as how velocity is speed in vector form), So displacement is measured in metres.
Other Units of Force:
There are two other units of force in Physics; however, they are not as commonly used as the SI unit of force Newton.
Dyne: A dyne is a force required to give a mass of 1 gram (1 g) an acceleration of 1 centimetre per second squared (1 cm/s²). 1 N = 100,000 dynes. You might use the dyne if you are working with very small objects.
Poundal and Pound: A poundal is a force required to give a mass of 1 pound (1 lb) an acceleration of 1 foot per second squared (1 ft/s²). 1 poundal = 0.1382 N. A pound is a force applied on a mass of 1 pound (1 lb) by the acceleration due to gravity, that is, g. It is a non-technical unit of force and is also referred to as the weight. These units of force are in the English system and are rarely used in scientific measurements.
Gram Force: It is defined as the force of standard gravity on a gram, that is, acceleration due to gravity (g)*gram.
Pond: It is another term for the gram force.
Sthene: It is defined as a tonne meter per second squared.
Ounce-force: An ounce-force is defined as the force of gravity on an avoirdupois ounce (mass = 1 ounce), that is, acceleration due to gravity (g)*ounce.
Ton-force: A Ton-force is defined as the force of standard gravity on 1 ton, that is, acceleration due to gravity (g)*ton.
Kip or Kipf: A Kip or Kipf is defined as 1000 pound forces.
What is Force?
Force is an external agent that is applied to a body to change the state of a body, speed of the body, direction of the body or position of the body. Force is a vector quantity, it has both magnitude and direction. The direction towards which the force is applied is known as the direction of the force and the application of force is the point where force is applied. It is measured using a spring balance and the unit in which force is measured in Newton(N).
What are the Effects of Force?
Change in state of the body of position
To change the speed of the body
To change the direction of the body
To accelerate the moving body
To decelerate or bring it to stop
Force Formula Derivation
Force is a product of mass and acceleration. It is a vector quantity that has both magnitude and direction.
F=ma
Where F= Force
m= Mass
a= Acceleration
Acceleration can be defined as the rate of change of velocity of an object in a particular specified time. It can be expressed as,
a= v/t
Where v= Velocity
t= Time
So, Force can be rewritten as,
F=mv/t
It is known that P=mv, where p is the momentum,
Therefore,
F= p/t = dp/dt
Force formula is helpful in finding out the force, mass, acceleration, momentum, velocity in any given problem.
Force is represented as,
Force = (Mass)(Acceleration)
Unit of force is Newton
Unit of Mass is Kilograms
Unit of Acceleration is Meter/second^2
Types of Forces
The two categories of forces are- Contact forces and non-contact forces
Forces that are directly in touch with the body where the force is to be applied or is in touch through a medium are known as contact forces such as muscular forces, mechanical force or frictional force.
Forces that act without any medium or any direct contact with the body are termed as non-contact forces and under these forces are Magnetic forces, Electrostatic forces, gravitational forces etc.
The International System of units is an internationally accepted metric system established in 1960, the standard for measurement which is approved by scientific researchers everywhere making it easier for people to understand or express the magnitude or quantity of a natural phenomenon.
SI units are important because they are based on precise standards and the base used in SI units is 10 which makes it easier for conversion.
There are a total of 7 base units and 22 derived units.
In the table given below is the base SI Units
S. No
Quantity
SI Unit
SI Unit Symbol
1
Length
Metre
m
2
Mass
Kilogram
kg
3
Time
Second
s
4
Electric Current
Ampere
A
5
Thermodynamic Temperature
Kelvin
k
6
Amount of substance
Mole
mol
7
Luminous intensity
Candela
cd
Other Units of Force
Force is measured in kilograms and is denoted by kg. However, there are also smaller measures called the cgs system. If we talk about force in a centimetre gram second system of unit CGS units, it is measured in dynes and is denoted as gf.