NEW! This pull-back bus smoothly accelerates from rest then decelerates to a smooth stop.  Travels approximately 2-5 meters depending on length of pull-back.  Attach a card to its rear bumper to produce graphs with a motion detector or attach ticker-timer tape to bumper for distance vs. time interval data.  Made of die-cast metal with moveable stop sign.  7" long.  Click on 'View Larger Image' for .jpg of position vs. time graph produced with a motion detector.