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Whats a KiloNewton?


Andy Collins
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To be a pedant, which is my natural state, 30kN does not equal 3000kgs.

 

30kN is, more or less, the force exerted by gravity on a mass of 3000kg (assuming the mass is on the surface of the earth). Actually, the force exerted on a 3000kg mass is about 29.4kN.

 

As to a 3t brake, that rather depends on what you mean by that. If you mean something capable of exerting a force of 30kN fair enough. But it takes a damn site more than 30kN to stop 3 tonnes dead if it's already moving at speed.

 

Confusion arises because we are basically very sloppy in our use of the terms 'force', 'weight' (which is the force exerted by gravity) and 'mass'. Likewise, we are sloppy with units. kg is a unit of mass, Newton is a unit of force (or weight).

 

If you have a climber with a mass of 75kg hanging still, the force gravity is exerting on them is about 735N, or less than 3/4 of a kN, and rope and krabs will be exerting a similar force to stop him plummeting.

 

If he falls 2m onto the system, the force exerted by the system needs to be sufficient to decelerate him, and that will be very much more. Exactly how much depends on how quickly he decelerates, which depends on a number of things, such as how elastic the rope is.

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well 30kn is used to measure 3000kgs so ill stick with it if i ask for a 29.4kn rating rope ill be told to nob off.

 

And stopping a moving object will increase its snatch weight amount of force depends on speed and weight and snatch ie no give more force some give in the system will reduce impact loading.

 

500kgs falling 20ft on 3 tonne rope will exceed the ropes limit and may break hence we use 8tonne rope for 500kgs eg.

 

But the answer is a kilonewton is another measure for kgs 1kn equals 100kgs not exact im sure but 99%

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