Terminal Velocity

Terminal Velocity is a GCSE physics game about falling objects and the forces that change their motion. Each round has ten questions in a mixed order. A Standard round has three graph questions, two resultant-force questions, two acceleration questions, two weight questions and one parachute question. The graph questions ask about the first terminal-velocity section, the greatest acceleration and the velocity in a flat section. The graph shows typical example values, not speeds every skydiver reaches: about 55 m/s before the parachute opens and 5.5 m/s afterwards. Downwards is positive.

A Challenge round has two graph questions, two resultant-force questions, two acceleration questions, one weight question, one parachute question and two terminal-velocity calculations. Those last questions use equal drag and weight to find either the drag or the object's mass. Later questions use larger and more varied values. Challenge starts with harder numbers.

Choose a letter for graph-section questions. Choose one of four answers for other questions. Letter answers have no unit. Every number has its unit, such as N, m/s, m/s² or kg. After you answer, read the working before moving on. A correct answer scores 10 points. Answer within 15 seconds for 5 extra points.

In Standard, the clock only removes the bonus. The question stays open after zero and a correct answer still scores 10 points. In Challenge, an unanswered question locks at zero and counts as wrong. Turn on Practice mode for ten questions without a timer. Press 1 to 5 for a graph answer or 1 to 4 for another answer. Press Enter to continue after the working appears. Your best scores stay on this device, with a separate score for Challenge.

When an object falls, its weight pulls it down towards Earth. Air resistance, also called drag, acts upwards. Drag grows as the object moves faster through the air. At release from rest, drag is nearly zero, so the resultant force is about equal to weight and acceleration is about g, or 9.8 m/s². The object then speeds up downwards.

As the object speeds up, air resistance gets larger. Weight stays about the same near Earth's surface. The difference between the downward weight and upward drag becomes smaller. The resultant force falls, so the object keeps speeding up but its acceleration gets smaller. It does not need a new downward force to keep falling.

Eventually the forces balance. In air, the upward push from the air is tiny, so drag is about equal to weight. The resultant force and acceleration are zero, so velocity stays constant. The object is still moving downwards. This steady falling speed is its terminal velocity. On a velocity-time graph, a flat section shows constant velocity. The steepest part of the rising curve has the greatest positive acceleration because its gradient is largest.

When a parachute opens, its larger area makes drag jump above weight. The resultant force points upwards while the skydiver keeps moving downwards and slows to a lower terminal velocity. As its speed falls, drag falls too. A steel ball bearing released from rest in glycerol also speeds up at first. Viscous drag grows with speed. Upthrust is an upward push from the liquid. At terminal velocity, the ball's weight equals drag plus upthrust. All forces balance.

The game uses weight = mass × gravitational field strength and acceleration = resultant force ÷ mass. It gives g = 9.8 N/kg in each calculation question. For an object falling through air, use weight minus drag for the downward resultant because air upthrust is tiny. If drag is larger, the resultant points upwards. At terminal velocity the resultant is zero, but the forces still act. The physics equation sheet can help you revise the equations and units.

AQA Physics 8463 names terminal velocity in section 4.5.6.1.5. It asks students to interpret velocity-time graphs and explain changing motion from forces. The linked weight and Newton's second-law outcomes are in 4.5.1.3 and 4.5.6.2.2. Terminal velocity is Physics-only in this AQA course. See the AQA Physics specification.

Edexcel Physics 1PH0 supports the calculations through velocity-time graphs in 2.10, free-fall acceleration in 2.13, Newton's first and second laws in 2.14 and 2.15, and weight in 2.16. Its specification does not name terminal velocity as a separate outcome. The Edexcel Physics specification gives those linked ideas.

OCR Physics A J249 names objects that reach terminal velocity in P2.2f. Its nearby outcomes cover uniform velocity in P2.2d, balanced forces in P2.2h, force and acceleration in P2.2i, and weight in PM2.3iii. OCR also suggests measuring ball bearings in glycerol. Read the OCR J249 specification for the course detail.

• On a velocity-time graph, a flat line means constant velocity. It does not mean the object has stopped.
• The steepest part of a rising curve has the greatest positive acceleration. A falling curve after the parachute opens shows deceleration.
• In air, upthrust is tiny, so drag is about equal to weight at terminal velocity. The object keeps moving.
• For an object falling through air, subtract drag from weight. State the direction as well as the force size.
• For acceleration, find the resultant force first. Then divide it by mass. Do not multiply by mass.
• After a parachute opens, the skydiver still moves downwards while slowing. The upward force does not mean upward motion.

Check the unit before choosing. A force uses newtons, mass uses kilograms and acceleration uses metres per second squared. A graph answer may be a letter or a velocity in metres per second.