Convert kilodyne to decanewton

The centimetre-gram-second system preceded the SI and its units linger in physics: the dyne is the force that accelerates one gram at 1 cm/s² (10⁻⁵ N), and the erg the work of one dyne over one centimetre (10⁻⁷ J), about the energy of a mosquito's wing beat. Astrophysics still writes luminosities in erg/s (the Sun: 3.8 × 10³³ erg/s), and surface tension is often quoted in dyn/cm, which equals mN/m.

Scales are marked in kilograms, but the kilogram measures mass, and weight is the force gravity exerts on that mass. The kilopond (kp, also written kgf) is the weight of one kilogram under standard gravity, 9.80665 N; it was a legal unit in Germany until 1978 and survives in older manuals. The pound-force (lbf) is the same idea for the pound, 4.448 N, and is still the everyday force unit in US engineering. The newton is the SI unit: a 100 g apple weighs about 1 N.

A newton is roughly the weight of an apple, of 102 g to be exact. Before the SI, force was measured in kilograms-force or kiloponds (kp), the weight of a kilogram, 9.81 N; old German torque figures in 'mkp' and towing limits in kp come from that era, and the pound-force (4.45 N) plays the same role in the US. The decanewton, 10 N, is popular in France, Italy and on lashing straps and slings precisely because it is almost a kilogram-force (1.02 kp), so 'LC 2500 daN' on a strap means about 2.5 tonnes. Climbing gear is rated in kilonewtons: a 22 kN karabiner holds about 2.2 t.