Abstract: The experimental principle of measuring Young＇s modulus by the dynamical method is studied systematically. The results show that the frequency which can be obtained from the experiment is the natural frequency of the system, which is composed of the metal bar and the changer, and the fundamental formula is deduced. The results also demonstrate that the frequency which is obtained in the experiment by using the extrapolation method is the natural frequency of the metal bar indeed.

Key words: Young＇s modulus, forced vibration, natural frequency, extrapolation, coupling