Question

A 50 N force causes a spring to compress 0.09 m.

Answer 1

What is the spring constant? What is the potential energy of the spring?​

$F=k\Delta x\to k=F/\Delta x=50/0.09=555.56\ (N/m)$

$PE=k(\Delta x)^2/2=555.56\cdot0.09^2/2=2.25\ (J)$