also, this I must share.  It comes right out of my physics text book * Ssithl prepares for brainmelt. A hockey puck, mass 0.115kg, moving at 35 m/s, strikes an octopus thrown onto the ice by a fan.  The octopus has a mass of 0.265 kg.  The puck and octopus slide off together.  Find the velocity. yeah, this is one that the authors put in for those students that stay up late trying to do these