Final answer:
The altimeter will capture when the helicopter is within 300 feet of the pre-selected altitude by measuring air pressure.
Step-by-step explanation:
In Physics, the term 'altimeter' is used to measure altitude. An altimeter is an instrument that determines the height above sea level or ground level. In this case, an altimeter will capture when the helicopter is within 300 feet of the pre-selected altitude. It can do this by measuring the air pressure around the helicopter and converting it into an altitude reading.