Final answer:
A motion sensor works by emitting a beam of infrared light and measuring the time it takes for the light to travel to an object and back. This allows it to calculate the position of the object.
Step-by-step explanation:
The motion sensor works by emitting a beam of infrared light and detecting the reflection of that light off of nearby objects. When the light beam hits an object, it reflects back to the sensor. The motion sensor measures the time it takes for the light to travel to the object and back, and uses this information to calculate the position of the object.
For example, if the motion sensor is used to measure the position of a glider on a track, it will send out a beam of infrared light towards the glider. The light will bounce off the glider and return to the sensor. By measuring the time it takes for the light to make this round trip, the sensor can determine the distance between the glider and the sensor, and therefore the position of the glider at that moment in time.