A load weighing m = 100 g is suspended to a rubber cord with a rigidity r = 25N / m.

A load weighing m = 100 g is suspended to a rubber cord with a rigidity r = 25N / m. The length of the cord is l = 26cm. Determine the length of the undeformed harness.

r = 25 N / m.
m = 100 g = 0.1 kg.
g = 9.8 m / s ^ 2.
l = 26 cm = 0.26 m.
l0 -?
l = l0 + x, l0 is the initial length of the bundle, x is the lengthening of the bundle.
l0 = l – x.
Fт = m * g, m is the mass of the load, g is the acceleration of gravity.
Fпр = r * х, r – harness stiffness, x – how much the harness has increased in length ..
Ft = Fpr.
m * g = r * x.
x = m * g / r.
l0 = l – m * g / r.
l0 = 0.26 m – 0.1 kg * 9.8 m / s ^ 2/25 N / m = 0.22 m.
Answer: the initial length of the bundle is l0 = 0.22 m.