Why does a forcemeter contain a spring?

A forcemeter contains a spring because it operates on Hooke's Law, which states that the force exerted by a spring is proportional to its extension or compression. When a force is applied to the forcemeter, the spring stretches or compresses, allowing the measurement of the force based on the amount of deformation. This mechanical property provides a simple and effective way to quantify force in various applications. The spring's ability to return to its original shape also ensures repeatability and accuracy in measurements.