Well, I wouldn't say the "curve is slowing"- thatcurveisn't moving at all!

But I know what you mean- the graph is "leveling off" or, technically, it is "convex downward". You should be completely sure that theslopeof the tangent line tells the rate of change of the distance, the velocity, and yes, because the tangent lines are getting less and less steep, the velocities are decreasing.'

I'm just not completely sure. Any help or hints would greatly be appreciated.