Let's consider the spring constant to be -40 N/m. Then the applied force is 28N for a 0.7 m displacement.
The formula to calculate the applied force in Hooke's law is:
F = -kΔx
where:
F is the spring force (in N);
k is the spring constant (in N/m); and
Δx is the displacement (positive for elongation and negative for compression, in m). Read more