Light gate

A light gate has a transmitter and receiver on opposite sides of a gap. A beam passes between them. Fit a rectangular card of measured length to a trolley so that the card interrupts the beam as the trolley rolls through the gate.

A light gate sends a beam towards a detector. A flag attached to a moving object interrupts the beam as it passes through the gate.

A trolley, ramp, blocks, metre rule, two light gates, datalogger, card and sticky putty can be used to investigate how ramp height affects average speed. Clamps and stands hold the light gates in place. The card fixed to the trolley interrupts each light-gate beam so that the datalogger can time the trolley's journey accurately.