Stretching springs

The springs and the pointer have no mass that matters, and every slotted mass is exactly 100 g or 50 g. Readings are to the nearest 0.1 cm with no scatter, and the pointer settles after one small bounce.

Spring A stays proportional for every load used here. Spring B follows k = 10 N/m exactly up to its limit of proportionality at 2.5 N, then stretches more for each extra load.

Real readings are taken in a lab; this is simulated apparatus.

With reduced motion each mass goes straight onto the hanger and the pointer jumps to its new reading.