The dynamic response of two-dimensional granular matter subjected to the impact of a spherical projectile is investigated experimentally and also numerically using discrete element method (DEM). The granular matter is modeled by the mono-disperse aggregation of nylon spheres arranged regularly and two-dimensionally in a rectangular container. The numerical simulations are compared with the experiments using high-speed video camera for the impact velocity of about 10 m/s. It is shown that the motion of each particle can be well simulated by discrete element method. Also. the dynamic response of the particulate aggregation is elucidated in detail by inspecting the distribution of velocity vectors of individual particles and contact forces between particles, and very distinctive behaviors are found.