b) Hooke's law

b) Hooke’s law

c) force constant k of a spring or wire; F = kx

Hooke’s law = before the limit of proportionality → x ∝ F

F = kx

• force (N) = force constant (Nm-1) x extension/compression (m)

force constant = the stiffness of a spring

for springs in series

• 1/k = 1/k₁ + 1/k₂ + 1/k₃…

for springs in parallel

• k = k₁ + k₂ + k₃…