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First and foremost is

The general terms and symbols used to define **mass** include: LOAD **m**, LOADED **m**, PAYLOAD **P** and RATING **R**, however, these do NOT apply internationally.

When we need to move the mass of a container from one place to another, sufficient force will have to be applied to overcome the resistance to want to be moved. Newton called this resistance "inertia" and became his 1st Law. He next gave us the equation to evaluate the magnitude of the force needed to overcome this inertia, his 2nd Law, the Law of Motion and is Force= mass(kg) x acceleration (m/s^{2})

or**F**=m**a**

where**F** and **a** are vectors,having both magnitude and direction,

whilst m is a scalar just stuff in this case.

Thus the units are kg m s^{-2} and named ** newtons** or simply **N**

after the great man.** Loading signifies Force.**

or

where

whilst m is a scalar just stuff in this case.

Thus the units are kg m s

after the great man.

Now in this equation acceleration is that due to gravity and is assumed to be constant around the world and taken as 9.81m/s^{2}. (The standard value for general use is 9.8m/s^{2} and for approximate use 10m/s^{2}) so the force required to lift 1kg is 9.8N and this is what is termed WEIGHT and should be stated in Force units N, but nobody does, nor does anyone ever ask for 4.9N of apples just half a kilo so we just carry on using kgs or lbs, as usual.

The resulting force due to gravity is known as a Body Force and acts throughout the mass towards the centre of the earth and in this form is difficult to manage, however, to simplify the problem the total resulting body force is considered to act at the mass centre, generally known as the Centre of Gravity (C of G) acting in the direction of acceleration, thus simplyfing the evaluation of all other forces involved when lifting anything.

For example when top lifting a container with a hook attached to a sling assembly, the force at the hook must equal the weight of the container expressed in N's but as already stated it isn't. Instead we use kg, or lbs, the unit of mass, so to differentiate weight (force) due to gravity from mass, the suffix g is added.Hence a container of mass m, Payload P plus Tare T, rated at R needs a force of R

If still confused, an elegant explanation is given at Weight or Mass

Mass unit of 1

lb

kg

Symbols

Short ton USA

2000

907

ST

Imperial (long) ton

2240

1016

Ton ton

Metric ton SI

2205

1000

tonne mt

Having precisely defined the units of mass, weight and force, in accordance with the 1993 ammendment, the units used on the CSC Safety Approval Plate, should be :

**Maximum Operating Gross Mass (GM) Units kg, kgs and lb, lbs** (Upper or lowercase)

Units same as GM above.

Slowly these units have been adopted as shown on this CSC plate for a container made in 2016. But many containers still bear the a mixture of units (in upper and lower case, singular and plural )

Finally, Newton's 3rd Law states that** To every action there is an equal but opposite reaction.** Lifting forces are the reaction forces, susceptible to failure, and to prevent this they have to be predicted and evaluated in order to select the appropriate gear and avoid failure. Having evaluated a Working Load Limit (WLL) or Safe Working Load (SWL) based on the all the known information, there are the famous **"unknown unknowns"** scenario where the lifting forces induced may be well in excess of those predicted and here is where the Factor of Safety (F of S) comes into play.