  We propose a new method to describe a recoiling D-brane that is elastically
scattered by closed strings in the non-relativistic region. We utilize the
low-energy effective field theory on the worldvolume of the D-brane, and the
velocity of the D-brane is described by the time derivative of the expectation
values of the massless scalar fields on the worldvolume. The effects of the
closed strings are represented by a source term for the massless fields in this
method. The momentum conservation condition between the closed strings and the
D-brane is derived up to the relative sign of the momentum of the D-brane.
