Understanding terminal velocity is really about tracking two forces and how they change relative to each other as speed increases.
Stage 1 — Just After Starting to Fall
Weight (downward) is much greater than drag (upward). The resultant force is large and downward, so the object accelerates rapidly at close to 10 m/s² (gravitational field strength, g).
Stage 2 — Speeding Up
As speed increases, drag increases too. This is because drag depends on speed — roughly proportional to speed squared for most objects. The resultant force is still downward, so the object still accelerates, but the acceleration is now smaller than before.
Stage 3 — At Terminal Velocity
Eventually drag equals weight. The resultant force is now zero. By Newton's Second Law (F = ma), if F = 0 then a = 0. The object moves at a constant velocity — this is terminal velocity.
It is important to note that the object is still moving and still falling — it just isn't speeding up any more.
This deep dive covers The Forces on a Falling Object — Step by Step within Terminal Velocity for GCSE Physics. Revise Terminal Velocity in Extra Topics for GCSE Physics with 13 exam-style questions and 11 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 2 of 13 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Terminal Velocity
An object reaches terminal velocity when falling through air. Which statement correctly describes the forces at terminal velocity?
Explain how a skydiver reaches terminal velocity after jumping from a plane. Include changes to forces and acceleration in your answer.