Identify the acceleration region by looking for the steep initial slope. This part shows the object speeding up as resistive forces are still small compared to weight.
Locate where the graph flattens out to determine terminal velocity. A horizontal line indicates zero acceleration and constant velocity, reflecting balanced forces.
Analyse sudden changes in slope to recognise events such as parachute deployment. A rapid negative slope implies strong deceleration due to a sudden increase in resistive force.
Freefall acceleration occurs when resistive forces are negligible, so the object accelerates at approximately . In contrast, terminal velocity arises once resistive force grows enough to cancel weight, stopping any further acceleration.
Constant speed vs. changing speed distinguishes terminal velocity from earlier motion. During freefall acceleration the velocity continually increases, but during terminal motion velocity remains steady due to balanced forces.
Terminal motion is defined by zero resultant force and therefore zero acceleration.
Sudden deceleration occurs when resistive force is abruptly increased, such as by opening a parachute. Terminal velocity graphs show this as a sharp negative slope followed by a new, lower terminal speed when forces rebalance.
Gradual reduction in acceleration occurs naturally as speed increases because resistive forces grow continuously. This is seen on graphs as a curve that becomes progressively flatter over time.
Always link the graph's slope to acceleration. Questions often ask why acceleration decreases, so explain how increasing air resistance reduces the resultant force.
Look for horizontal sections to identify terminal velocity. Examiners commonly expect students to explicitly mention that a flat line means zero acceleration due to balanced forces.
Clearly explain sudden slope changes, especially negative slopes. In exam contexts, emphasise the force imbalance that causes deceleration and describe how a new terminal velocity forms.
Confusing velocity with acceleration is a frequent error. A rising velocity does not always mean constant acceleration, and students sometimes forget that curvature on a graph indicates changing acceleration.
Misinterpreting a flat line as the object being stationary instead of moving at terminal speed can occur. It is crucial to remember that on a velocity–time graph, a horizontal line means constant velocity, not zero velocity.
Ignoring changes in resistive forces leads to misunderstanding terminal velocity formation. Many learners mistakenly assume acceleration stops suddenly, rather than decreasing smoothly as resistive forces increase.
Fluid dynamics provides deeper explanations for resistive forces, showing how drag depends on speed, cross‑sectional area, and fluid density. These ideas connect terminal velocity to engineering problems like designing safer parachutes.
Newton’s laws underpin all interpretations of velocity–time graphs, making terminal velocity an essential application of force balance and proportional acceleration.
Energy considerations extend the concept, since during terminal velocity the gravitational potential energy lost per second equals the work done against resistive forces. This highlights the wider energy flow in falling motion.
