A certain bungee cord can be modelled by attaching a rope of 25m to a spring of equilibrium length 15m and a spring constant of 4*10^2 N/m. If the rope end of the bungee cord is attached to a point 70m above the ground, what is the maximum mass of a person who can safely jump with it?
F = kx
and you want x < 70-25-15
F < 400*30 = 12000 N = 1223 kg
that doesn't seem reasonable. Better check my math