This topic summary covers Knowledge Organiser: Terminal Velocity 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 13 of 13 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Terminal Velocity
Key Terms
- Terminal velocity — constant speed when drag = weight
- Drag — resistive force opposing motion through a fluid
- Resultant force — net force after all forces added
- Weight — W = mg (downward gravitational force)
- Streamlining — shape designed to reduce drag
The Sequence to Terminal Velocity
- Weight > drag → resultant force down → acceleration
- Speed increases → drag increases
- Resultant force decreases → acceleration decreases
- Weight = drag → resultant = 0 → acceleration = 0
- Constant velocity = terminal velocity
V-T Graph Features
- Steep curve → decreasing curve → horizontal line
- Gradient = acceleration
- Area under graph = distance
- Parachute opening: steep negative gradient → new lower horizontal line
Factors Affecting Terminal Velocity
- Larger surface area → lower terminal velocity
- More streamlined → higher terminal velocity
- Greater weight/mass → higher terminal velocity
- Denser fluid → lower terminal velocity
Key Equations
- At terminal velocity: weight = drag force (resultant force = 0)
- F = ma (before terminal velocity, resultant force causes acceleration)
- Drag force ∝ v² (drag increases with the square of speed)
- W = mg (weight in Newtons from mass and gravitational field strength)
Common Mistakes
- Saying the object stops accelerating because forces disappear: At terminal velocity, forces are still acting — weight and drag are equal and opposite, giving zero resultant force, not zero force
- Thinking terminal velocity is the maximum possible speed: Terminal velocity depends on the specific conditions (shape, mass, fluid density) — a more streamlined object or greater mass gives a higher terminal velocity
- Confusing the velocity-time graph shape: The v-t graph for a falling object curves upward (decreasing gradient) before becoming horizontal at terminal velocity — the gradient (acceleration) decreases to zero, not the speed
- Saying drag increases linearly with speed: Drag force increases with the square of speed (∝ v²) — doubling speed quadruples drag, which is why terminal velocity is reached
- Forgetting the parachute phase on a skydiver graph: When a parachute opens, drag suddenly exceeds weight — the skydiver decelerates until a new (lower) terminal velocity is reached
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.
Quick recall flashcards
What is terminal velocity?
The constant velocity reached when drag force equals weight, so resultant force = 0 and acceleration stops
Why does terminal velocity occur?
As an object speeds up, drag increases. Eventually drag = weight, resultant force = 0, so acceleration stops (F = ma)