the stretch of a spring in millimeters is proportional to

the force applied to it. Mathematically, we can represent this relationship with the equation:

Stretch (mm) = k * Force (N)

Where:
- Stretch is the amount by which the spring extends or compresses in millimeters.
- Force is the magnitude of the force applied to the spring in Newtons.
- k is the proportionality constant, known as the spring constant, which varies for different springs.

In this equation, the proportionality symbol (∝) is replaced with an equality sign (=) since the proportionality is exact when k is constant.