The Fixie kids find it a real challenge to sneak past Elisa and get back to Professor Eugenius with a spare part without setting off the motion sensor that automatically opens the door to the laboratory. Insert 1: How does a motion sensor work? Insert 2: Different uses for sensors.

Originally released by Ooom, Llc., 2014. Streaming video file encoded with permission for digital streaming by Infobase on May 16, 2016.