Definition
The constant maximum speed reached by a falling object when the drag force from the surrounding air exactly balances the force of gravity, resulting in zero further acceleration.
Plain English
The fastest speed something can fall through the air. Once gravity pulling it down and air resistance pushing back are equal, it stops speeding up and falls at a steady rate.
Context Anchor
Seen in weather and engine water ingestion discussions, especially when describing how fast heavy raindrops can be moving when they enter an aircraft engine inlet.
Derivation
From Latin terminus, meaning 'end' or 'limit,' and velocitas, meaning 'speed.' So terminal velocity literally means 'limit speed' — the speed beyond which the object cannot accelerate while falling.
Why Pilots Care
Determines maximum descent rate without power and affects calculations for emergency procedures or falling objects near the aircraft.
Grounding Statement
Drop a stone and it keeps speeding up — but only for a while. Air pushes back harder the faster it falls, until the push back equals gravity. From that moment on, it falls at a steady speed: its terminal velocity.
Intuition Check
Terminal does not mean an airport building or the end of a flight here. It means the limit of how fast something will keep falling through the air under those conditions.
Example Sentence 1
Large raindrops reach terminal velocity quickly, which is why heavy rain can hit the windshield and engine inlet with significant force.
Example Sentence 2
At terminal velocity the forces on the falling object are equal, so speed no longer increases.