For relatively light objects at low velocities (2 kg falling from 1 meter qualifies), you could probably take the load and deflection as those resulting from an object of twice the weight. It is roughly equivalent to Timoshenko's observation that axially-loaded rods which receive a suddenly-applied load elongate twice as much as a when a static load of equal weight is on the rod. The extrapolation is that applying a load that is twice as heavy simulates this effect.
Higher velocities,and intuitively I'd say that a very heavy object relative to the mass/inertia/resistance of the beam, confounds this approach. At some point you have to get to energy equations and the local yielding of materials. I had a client who was accidentally asking about objects falling at terminal velocity. When I told him that they would penetrate the steel, he realized that he had not asked the right question, since the objects would be falling less than 10 feet.
