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What Is The Si Unit Of Force In Physics

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Commonly Seen As Kilonewtons

Units of Force – CGS and SI Units (Physics Class 10)

It is common to see forces expressed in kilonewtons , where 1 kN = 1000 N. For example, the tractive effort of a Class Y steam train locomotive and the thrust of an F100 jet engine are both around 130 kN.

One kilonewton, 1 kN, is equivalent to 102.0 kgf, or about 100 kg of load under Earth gravity.

1 kN = 102 kg × 9.81 m/s2.

So for example, a platform that shows it is rated at 321 kilonewtons , will safely support a 32,100-kilogram load.

Specifications in kilonewtons are common in safety specifications for:

Derivation Of Si Unit Of Force In Physics

To derive the SI unit of force in physics, we need to remember the formula of force which is defined as

F= m× a

First, we derive the SI unit of acceleration using its formula which is defined as


where v Change in velocity

t Change in time

Now, we write the SI unit of velocity and time in the formula of acceleration


Hence, the SI unit of acceleration

a= msec-2

Now, we put the SI unit of acceleration and mass in the formula of force

F= kg× msec-2

Hence, the SI unit of force is given as

F= kg msec-2 or Newton

Other unit of forceOther than SI unit, force is also measured in different units depending upon the system of measurements which are given below :

  • Dyne
  • Symbol – dyn

    1 dyn=10-5N

    1 dyne is defined as the force can be measured by required accelerate of 1 gram of mass at an acceleration of 1 centimeter per second. It is the unit of force in CGS system of units and it is primarily used in measuring surface tension.

  • Gram- force
  • Symbol – gf

    1 gf=0.0098 N

    1 gram- force is defined as the force required to accelerate 1 gram of mass at acceleration equal to the acceleration due to gravity. It is the gravitational unit of force in CGS system of units.

  • Poundal
  • Symbol – pdl

    1 pdl= 0.1382 N

    1 Poundal is defined as the force required to accelerate 1 pound of mass at an acceleration of 1 foot per second. It is the unit of force in the FPS system of units and this system is commonly used in civil engineering and construction engineering.

  • Pound- force
  • Formulas For Work And Power

    The word work has a different meaning in the world of Physics. In Physics, work done is given by force applied on an object to move a distance , and its formula is:

    W = F * d.

    Even after applying a lot of force, if an object does not move, then in the eyes of a physicist, no work is done.

    The word power is also used differently by physicists. Power is the ratio of work and time, i.e. the time taken to complete a work gives the power of an entity. It is expressed mathematically as:

    Power = Work/Time or P = W/t.

    Power is the rate at which work is done, and it is also the rate at which energy is transferred. While studying electricity, you would find the power is defined as:

    Power = V * I, where V is the voltage within the circuit, and I is the current through the circuit.

    We could derive another formula for power from the formula for work. Since Work = force * distance and power = work/time, then power = /time. Now we know that velocity = distance/time hence:

    Power = force * velocity = F * V

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    Force And Motion: Relation Si Unit Formula

    We define force as that external push or pull acting on an object which changes or tends to change the state of rest or state of a uniform linear motion of the object. A force may also deform an object. In physics, we encounter various body movements. What causes the movement of an object? The answer is powerful. What is stopping the moving object? The answer is Force. Thus, in general, force and motion are similar to the two sides of a coin. For example, the relationship between force and movement is seen in throwing a ball and catching the ball.

    Table of Content

    How To Measure Work Done

    What is the S.I. unit of force?

    In everyday life, we consider work to be a synonym of effort, labour, toil, or energy spent. However, the term work is entirely different from all these terminologies.

    The work done is measured in Joules denoted by J. The amount of work done is calculated by multiplying the force by the amount of displacement of an object.

    Work done in different ways are described below by example

    Consider a box, when a force F is applied to displace a box from one position X to Y by a distance S, then work done will be W = F . S

    Where work is a scalar quantity with no direction.

    Work Done by a Constant Force

    When a constant force F acting on the object produces a displacement S in that body, then work done by the force is the dot product of the force and displacement given by,

    W = F . S

    If is an angle between F and S, then from eq,

    W = F S Cos

    Which means the two vectors F and S are in the same direction.

    If = 90°, then,

    W = 0

    No work will be done as the force applied is in a direction perpendicular to the distance. It states that the body under the action of multiple forces is equal to the work done by the resultant force. Hence the body is at equilibrium.

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    What Is The Si Unit

    SI unit is an international system of measurements that are used universally in technical and scientific research to avoid the confusion with the units. Having a standard unit system is important because it helps the entire world to understand the measurements in one set of unit system. Following is the table with base SI units:

    Sl. No.

    What Is The Unit Of Force

    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 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 Newtons Second Law of motion, force is equal to the rate of change in momentum . We also know that momentum is the product of mass and velocity .

    Force = Rate of change of momentum

    = P/ t

    = mv/ t

    Force= mass*velocity / time —

    Newton = /sec²

    Unit of time = Second

    Unit of velocity = Metre / Second

    NOTE: Velocity is Displacement by time. Displacement is the shortest distance from the initial to the final point. Inshort,displacement is distance in vector form, So displacement is measured in metres.

    NOTE: Velocity is Displacement by time. Displacement is the shortest distance from the initial to the final point. Inshort,displacement is distance in vector form, So displacement is measured in metres.

    Other Units of Force:

    What is Force?

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    What Is The Unit For Momentum In Physics

    unitmomentumunits ofunitsmomentum

    . Besides, what is a momentum in physics?

    Momentum is a physics term it refers to the quantity of motion that an object has. A sports team that is on the move has the momentum. Momentum can be defined as “mass in motion.” All objects have mass so if an object is moving, then it has momentum – it has its mass in motion.

    how is the unit of momentum derived? If you know momentum’s definition, you are able to figure out the units! Momentum = p =mv = mass times speed . Units p then are = kilogram * meter / seconds.

    Likewise, what is the SI unit of force and momentum?

    Momentum is Force x Time so has units of Newton Seconds Or kilogram meters per second . ‘N’ is the S.I.unit of force . And Kgm/s is the S.I.unit of momentum.

    What is force formula?

    The formula for force says force is equal to mass multiplied by acceleration . Force is measured in Newtons , mass in kilograms , and acceleration in meters per second squared .

    What Is The Line Of Action Of A Force

    What is the SI unit of force? | 9 | FORCES AND LAWS OF MOTION | PHYSICS | PRADEEP | Doubtnut

    The line along which a force is acting on an object is called the line of action of the force. The point where the force is acting on an object is called the point of application of the force. The force which opposes the relative motion between the surfaces of two objects in contact and acts along the surfaces is called the force of friction.

    Galileo experimentally proved that objects that are in motion move with constant speed when there is no force acting on it. He could note that when a sphere is rolling down an inclined plane, its speed increases because of the gravitational pull which is acting on it.

    When all the forces acting on an object are balanced, the net force acting is zero. But, if all the forces acting on a body result in an unbalanced force, then the unbalanced force can accelerate the body, which means that a net force acting on a body can either change the magnitude of its velocity or change the direction of its velocity. For example, when many forces act on a body, and the body is found to be at rest, we can conclude that the net force acting on the body is zero.

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    Physics All Measurement Quantities Their Base Si Units And Symbols

    kilogram square meter per secondkg m2s-1
    newton second per square meterN.s.m-2
    watt per meter per degree celciusWm-1C-1
    joule per kilogram per Kelvinj kg-1K-1

    A physical unit is the chosen standard used for measuring a physical quantity. it should be:-

  • Well defined
  • independent of changes in physical conditions
  • Types of the system of units

    there are the following internationally accepted systems for measuring the units:


    physical units are of two types:

  • fundamental units
  • derived units
  • Si Unit Of Force And Work

    A body like spring has potential energy stored in itself and when it is stretched from its mean position, it starts vibrating to and fro. The more the force is applied, the more is the displacement and more will be the restoring force acting within in the spring.

    Therefore, the restoring force F is measured in Newton .

    The dimensional formula is given by .

    The work done by the spring to come back in its mean position is measured in Newton-meter or Joule and its dimensional formula is given by .

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    Relationship Between Force And Motion

    Force and motion are closely linked with nature. We can say that force is the cause of movement. Suppose there is a movement, we can say that there must be some force at work or there must be some force at work that produces this movement. When a person is walking, therefore moving, there must be some active force in it that makes him move. What is this force? This force is the muscle strength of his body.

    Before we get into the relationship between force and movement, lets take a quick look at what energy means. Simply, a force can be pushed or pulled. Force is defined as any interaction that, if not challenged, will change the movement of an object. By the definition itself, it is clear that the force affects the state of the movement of an object.

    But what exactly does a state of motion mean? In physics, motion is defined as a change in position relative to time. In simple terms, movement refers to physical activity. In general, motion can be defined as,

    • Change the speed, though
    • Change direction.

    Sir Isaac Newton was the first to discover the link between motion and force. From his practical lessons and the laws of motion we can come to the following three conclusions:

    • Force can speed up the body
    • Force can change the direction of a moving body

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    • Application of force can make a body at rest move.
    • Force can change the direction of the moving object.
    • The turning effect is either clockwise or anticlockwise.

    Parallelogram Rule For The Addition Of Forces

    si and cgs units

    A force is known as a bound vectorâwhich means it has a direction and magnitude and a point of application. A convenient way to define a force is by a line segment from a point A to a point B. If we denote the coordinates of these points as A = and B = , then the force vector applied at A is given by

    ) , =\mathbf _+\mathbf _=2=2,}

    where E is the midpoint of the segment BD that joins the points B and D.

    Thus, the sum of the forces F1 and F2 is twice the segment joining A to the midpoint E of the segment joining the endpoints B and D of the two forces. The doubling of this length is easily achieved by defining a segments BC and DC parallel to AD and AB, respectively, to complete the parallelogram ABCD. The diagonal AC of this parallelogram is the sum of the two force vectors. This is known as the parallelogram rule for the addition of forces.

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    Development Of The Concept

    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. In part this was due to an incomplete understanding of the sometimes non-obvious force of friction, and a consequently inadequate view of the nature of natural motion. A fundamental error was the belief that a force is required to maintain motion, even at a constant velocity. Most of the previous misunderstandings about motion and force were eventually corrected by Galileo Galilei and Sir Isaac Newton. With his mathematical insight, Sir Isaac Newton formulated laws of motion that were not improved for nearly three hundred years. 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.

    Aristotelian physics began facing criticism in medieval science, first by John Philoponus in the 6th century.

    In the early 17th century, before Newton’s Principia, the term “force” was applied to many physical and non-physical phenomena, e.g., for an acceleration of a point. The product of a point mass and the square of its velocity was named vis viva by Leibniz. The modern concept of force corresponds to Newton’s vis motrix .


    What Are The Effects Of Force

    In physics, motion is defined as the change in position with respect to time. In simpler words, motion refers to the movement of a body. Typically, motion can either be described as:

  • Change in speed
  • The Force has different effects and here are some of them.

    • Force can make a body that is at rest to move.
    • It can stop a moving body or slow it down.
    • It can accelerate the speed of a moving body.
    • It can also change the direction of a moving body along with its shape and size.

    So Force can be articulated as:

    F = mv/t

    Inertia formula is termed as p = mv which can also be articulated as Momentum.

    Therefore, Force can be articulated as the rate of change of momentum.

    F = p/t = dp/dt

    Force formulas are beneficial in finding out the force, mass, acceleration, momentum, velocity in any given problem.

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    Definition: Force And Motion

    To understand what force is, we need to think about gravity. Pushing and pulling apply to an object or force such as movement or an attribute of physical activity is defined as a force. It is like pushing and pulling, words like squeezing and stretching also define the concept of what energy can do. This is especially so when two parties are in contact. Based on Newton’s universal law of gravity, everything in the universe has been forced over other things. Thus, a force may start motion in an object which was at rest. The SI unit of force is Newton or kg.m/s². The measuring quantity of force is a vector.

    Force is associated with the motion of translation when an object is moving in a certain direction. However, under such conditions, energy can transform an object into a specific axis. This is known as the turning effect of a force.

    In simple terms, whenever the body moves, we say that it is in motion. For example, if a boy is walking down the street from the school to home, we could say that the boy is moving. But imagine if a boy stops for 5 minutes on the road and sits down. If someone immediately asks if the boy is moving, the answer will be no. In this regard, we can conclude that physical activity is time-dependent. In physics, we say that movement is a change in a physical state in terms of time.

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