An aerospace engineer is testing a landing gear shock-absorbing tension spring. The spring is suspended vertically from a rigid ceiling, as shown in the diagram below.
A horizontal reflective target plate is attached to the bottom of the spring. A laser distance sensor positioned on the floor directly below measures the vertical distance, ddd, to the underside of the target plate.
With no load attached, the spring is straight but unstretched, and the engineer records an initial distance reading of d0d_0d0.
Describe how the engineer can determine the extension of the spring each time a new mass is suspended below the target plate.