In the rope access industry everything is rated in kn of force. We can directly equate this to 100 kg when looking at working load limits on the slings in which we use to hang off of. Everyone always says you don’t need to know why, you just need to know that it does. I would like a simple way of explaining it to the new people coming into my industry.
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Newtons (N), and extended units like kiloNewtons (kN), are units of force. When we talk about weight, we are usually talking about the force which is exerted by a mass in a gravitational field, although you could also be talking about the force exerted by an object which is accelerating (e.g. in an elevator). So, your weight can change. You weigh less on the moon, and you weigh more in an accelerating rocket. Your weight is dependent on the acceleration you are experiencing. Your mass, however, does not change. 1 kg on Earth is 1 kg on the moon is 1 kg in the rocket. At the Earth’s surface, at sea level, the average gravitational acceleration is 9.80665 m/s^2 . So, your 1 kN of force corresponds to (1000.00 N) / (9.80665 m/s^2 ) = 101.972 kg. This is approximately a factor of ten.
Note that this applies in the static case for an object subject to gravity, but in rope work, you also have to deal with dynamic effects. A falling mass being brought to a stop by a rope in a short period of time corresponds to a large acceleration, and thus large forces which the rope system must sustain.
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