Why do spring balances show wrong readings of weight after they have been used for a long time?

(N/A) spring balance works on the principle of Hooke's Law,which states that the extension of a spring is directly proportional to the applied force within the elastic limit. After repeated use over a long period,the spring undergoes elastic fatigue. This means the material of the spring loses its original elastic strength and may undergo permanent deformation. Consequently,the spring does not return to its original shape or length when the load is removed,leading to incorrect readings.