An instrumented falling weight impact test is thoroughly investigated in two cases, that of a rebound and that of a rupture in the sample. First, the force signal is analyzed with four methods: the continuous wavelet transform (with different wavelets: derivatives of a Gaussian and Morlet's), the Gabor transform, the WignerVille transform and the classical Fourier analysis. It is shown how a proper use of the timefrequency methods allows to precisely detect the discontinuities in the signal, the moment of rupture, if any, and the frequencies that are excited at the impact. In a second part, modal and stress analyses are carried out, both by an analytical method and by finite element computations. The results confirm those obtained in the first part and agree with experimental findings.