[en] The total energy deposited by collimated monoenergetic projectiles in a Si telescope, distinguish those undergoing nuclear reactions from those stopped entirely by ionization. Energy-deposition spectra of 49.9.4 MeV ¹⁰C projectiles were measured by injecting magnetically separated, focused, monoenergetic, identified secondary beams of those projectiles into a Si detector telescope at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University. Using those data, we calculated total reaction cross section, σ_R=1.55 b, which is constant for energies ranged from 100 to 500 MeV. Our result was practically identical with that obtained by simple geometric model. In addition, on the basis of the preceding conclusions, we carried out Monte-Carlo simulation of one energy deposition-spectrum. (authors)