A Level Physics Practice Exam

Which point on the stress-strain graph indicates the yield point?

1. The limit beyond which the material deforms plastically

2. The maximum stress the material can withstand

3. The point at which the material exhibits no further strain

4. The point where the material breaks

The correct answer is: The limit beyond which the material deforms plastically

The yield point is indicated by the limit beyond which the material deforms plastically. This is the critical point on a stress-strain graph where the material starts to experience permanent deformation. Up until this yield point, if the material is subjected to stress and subsequently unloaded, it will return to its original shape. However, once the stress exceeds this point, any deformation caused will not be fully recovered, and the material will not return entirely to its initial state. This concept is fundamental in materials science and engineering because understanding the yield point helps in predicting how materials will behave under different stress conditions and ensuring that structures are designed within safe limits to avoid permanent deformation.