http://www.whyalla4wd.org.au/Shackles.htmlDetermine Speed of Shackle if Snatch Strap Breaks.
If all the Elastic Energy of the Snatch Strap is transferred to Kinetic Energy in the Shackle then the peak Speed of the Shackle as the Snatch Strap returns to it's 9.0m length can be determined. (Assuming no losses due to friction)
From Energy Conservation,
Elastic Energy in Snatch Strap = Kinetic Energy of Shackle
PEStrap = KEShackle
1/2 k x2 = 1/2 m v2
where k = spring constant
x = distance stretched (meters)
m = mass of shackle (kg)
v = velocity of shackle (m/s)
1/2 (20750N/m) (0.579m)2 = 1/2 (0.68kg) v2
v = 101m/s
or Peak Speed of Shackle v = 364 km/h