Terminal velocity means zero acceleration, not zero forces
- 01
The tempting model
Assuming a falling object at terminal speed has no forces acting.
- 02
Why it feels right
No acceleration sounds like nothing is happening dynamically.
- 03
Where it breaks · how to catch it
You erase gravity when drag balances it.
- 04
The correct model
At terminal velocity, net force is zero because drag equals weight. Gravity and drag still act; they balance.
- 05
Repair · see it, then test it
worked example A skydiver falls at terminal speed. What is the net force?
Tempting move
mg downward because the skydiver is still falling.
Correct move
Zero net force; drag upward equals mg downward.
Test the repair NL-16 · transferMake a fresh prediction before referring to the worked example.