Force Measurement Basic Knowledge

●What is Force Measurement?

Force is usually measured by applying it to a calibrated measuring instrument which resists the force and indicates or records its magnitude.

A force gauge is a small measuring instrument used across all industries to measure the force. It can be used for material characteristic evaluation, tactile, operability of accelerator/brake pedal tests and so on.

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●What is Force?

In physics, force is a quantitative description of an interaction that causes a change in an object’s motion. Force is a vector quantity, with both direction and magnitude. It is defined as Mass x Acceleration = Force. The SI unit of force is the newton (N); defined as the unit of force which would give to a mass of one kilogram an acceleration of 1 meter per second squared. There are a lot of force types including tension, compression, shearing, bending, and friction.

Newton’s Universal Law of Gravitation states that any two objects exert a gravitational force of attraction on each other. The gravitational acceleration of earth is defined as g=9.80665m/s2 (standard value) by International Committee of Weights and Measures. For example, the weight of 1kg mass at earth is nearly equal to 1(kg)×9.8(m/s2)=9.8(N).

●What is Torque?

Torque is a measure of how much a force acting on an object causes that object to rotate. Torque is defined as Force (F) x Distance (r) = Torque. The distance (r) is from the pivot point to the point where the force acts. The SI units of torque is a Newton-meter (N・m).

Imagine pushing a door to open it. The force of your push (F) causes the door to rotate about its hinges (the pivot point). How hard you need to push depends on the distance you are from the hinges (r). The closer you are to the hinges (i.e. the smaller r is), the harder it is to push.

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●Unit of Force: N (Newton)

It is said that a British physicist Isaac Newton came up with the Law of Universal Gravitation, watching an apple falling. It seems not true that the falling apple led him the idea, yet “Newton” as a unit of force was named to respect his contribution to development of science. In Japan, “N(Newton)” is only allowed to use in force measurement due to Measurement Act of Japan. However, kgf (kilogram force), lbf (pound force), and ozf (ounce-force) are also used in other countries.

For Example 1kgf ≒ 9.8N(Approx. 10 times)

1N ≒ 0.2248lbf

1lbf ≒ 16ozf

●Unit of Torque: N・m (Newton meter)

In Japan,  “N・m” and “N・cm” are allowed to use in torque measurement due to Measurement Act of Japan. However, kgf・m and lbf・in are also used in other countries.

For Example 1N・m = 100N・cm

1N・m ≒ 0.1kgf・m

1N・m ≒ 8.85lbf・in(1in = 0.254m)

●Measurement Unit(N)by Measurement Act in Japan

The followings are units which are provided by Measurement Act in Japan.

Quantity of state of

physical phenomena

Symbol Measurement Unit
Force N Newton
Moment of force N・m Newton meter
Pressure Pa, N/m2, bar Pascal, Newton per square meter, and Bar
Stress Pa, N/m2 Pascal, Newton per square meter
Viscosity Pa・s, N・s/m2 Pascal second, Newton second per square meter

* Force conversion 1kgf=9.80665N

●SI Prefix

To avoid the regular use of very long numbers, SI (the international system of units) encourages the use of multiples of 1 000, (expressed as 103 in scientific notation) for large numbers, and multiples of 0.001 (or 10-3) for small numbers. Each of these multiplying factors has a specific symbol, some of which are shown in the below table.

Symbol SI prefix Scientific notation
N nano 10-9
μ micro 10-6
m milli 10-3
c centi 10-2
da deca 10
k kilo 103
M Mega 106
G Giga 109

For Example 1N = 100cN = 0.1daN

100kgf ≒ 1000N = 1kN = 100daN

1N・m = 100N・cm = 100cN・m