(first part_Young's modulus)
1.Using the Hook’s law within elastic limited length, the ratio of stress to strain should be a constant.
2.To Pull or compress a elastic rod object, the ration of stress to strain should keep a constant. That is, Young’s modulus.
3.The purpose of this experiment is to learn optical level and to measure the Young’s modulus of metal line.
4.The operation and theory of optical level.

(second part_Torsion pendulum_shear modulus)
1.Solid object has some degree of elasticity. Its volume could be little changed through pushing, pulling or pressing.
2.Shear stress is the cause of the bearing strain during loaded rotating, and the cause of the facture.
3.Torsion pendulum is used to measure the period of vibration object, and to calculate the shear modulus of a metal rod.