We report the results of a radial velocity survey of planetary nebulae (PNe) located in the tidal features of the well-known interacting system NGC 5194/95 (M51). We find clear kinematic evidence that M51s northwestern tidal debris consists of two discrete structures which overlap in projection -- NGC 5195s own tidal tail, and diffuse material stripped from NGC 5194. We compare these kinematic data to a new numerical simulation of the M51 system, and show that the data are consistent with the classic ``single passage model for the encounter, with a parabolic satellite trajectory and a 2:1 mass ratio. We also comment on the spectra of two unusual objects: a high-velocity PN which may be associated with NGC 5194s halo, and a possible interloping high-redshift galaxy.
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