Help your child relate the balance point to changes in the plane’s pitch and flight.
Choose a wing shape. Watch where your plane lands.
The wings push on the air, and the air pushes back. Air resistance slows the plane. Its balance point changes how the nose turns. A steep climb can leave it too slow to glide smoothly.
Stay with your child throughout the experiment. Read the task together, compare your predictions and start the test. Operate the controls, then discuss what changed.
Explain that the percentage locates the balance point: a bigger number moves it back from the nose. Compare several real throws because hand launches and paper folds vary.
Ask: “What did you change? What did you notice? What will you try next?” A different result is a clue, not a bad score.
This is a simple pretend-paper plane with assumed wing settings. Use it to compare ideas; your own paper fold may fly a different distance.
Use the simulation to discuss patterns. You remain responsible for choosing and supervising any physical activity; real results can differ.
Why should we compare several real throws instead of choosing only the best one?
The balance-point percentage is a position, not a quality score. A larger value moves it rearward. Real folds and hand launches vary.
2D rigid glider in still air, mass 5 g. Lift L = ½ρv²S·CL and drag D = ½ρv²S·CD, with ρ = 1.225 kg/m³. Lift is perpendicular to velocity; drag opposes it. Before ±15° incidence, CL = 0.15 + 3.5α (radians); beyond that, lift rolls off with a cosine. CD = CD₀ + CL²/(π·0.75·AR) + 0.9sin²α. Pitch moment coefficient = 0.035 + (CG − 0.30)CL − 0.12q·c/(2v). I = mc²/12. Numerical integration uses RK4 with a 0.0025 s step and interpolates ground contact. Wing dimensions and coefficients are assumed teaching values, not measured paper-plane data. No wind, bending, yaw or roll. The drawing is a readable schematic, enlarged relative to the flight distance. Range is an estimate, not a prediction for a particular fold.
Classic: S = 0.018 m², span = 0.19 m, chord = 0.18 m, CD₀ = 0.045. Dart: 0.012 m², 0.12 m, 0.24 m, 0.040. Glider: 0.024 m², 0.27 m, 0.15 m, 0.050. The balance control specifies the assumed chordwise centre of mass.
NASA · Forces on a glider · Lift equation · Drag equation
Sources explain the physical relationships. The chosen model parameters and simplifications are listed above.
Quick guide: s = seconds · m = metres · cm = centimetres · g = grams · kg = kilograms.
The wings turn moving air into an upward force called lift. Air resistance slows the plane down. A steep climb can leave it too slow to keep flying smoothly. The balance point also changes how the nose turns.
Fold two planes from the same paper. Use a small paperclip to change the balance point. Throw gently along a clear indoor space, away from faces. Measure five flights of each design; compare the average and the spread.