Question

An elastic cord was stretched to its elastic limit by a load of 2N. if 0.35cm length of the cord is extended to 0.6cm by a force of 0.5.What will be the length of the cord when the stretching force is 2.5N?

Answer 1

hard to say, since the force will try to extend the cord past its elastic limit.
It will either break or stop stretching or become damaged so it will not return to its original length on release.

or maybe the initial sentence does not apply to the cord described later, since that cord obeys
0.5N = (0.6-0.35)k
k = 2 N/cm
so if F = 2.5 N,
2x = 2.5
x = 0.8
and 0.35 + 0.8 = 1.15 cm