Springs and Elastic Energy
Hooke's Law: F = kx, where k is the spring constant (stiffness, in N/m) and x is compression or extension from rest (in meters). A stiffer spring has a larger k.
Elastic potential energy stored in a spring: PE = ½kx²
Example: Spring with k = 200 N/m compressed 0.1 m: PE = ½ × 200 × 0.01 = 1 J.
Doubling the compression quadruples the stored energy (x is squared).