H1 Physics 8867 · objective lesson
Air resistance and terminal velocity
As a body falls, gravitational potential energy decreases; kinetic energy rises while it accelerates and energy is transferred thermally by drag. At terminal velocity weight and drag balance, acceleration is zero and kinetic energy is constant, but gravitational potential-energy loss continues to be transferred to thermal stores.
Repair the common break
Common misconception: At terminal velocity no forces act and no energy is transferred.
Correct model: As a body falls, gravitational potential energy decreases; kinetic energy rises while it accelerates and energy is transferred thermally by drag. At terminal velocity weight and drag balance, acceleration is zero and kinetic energy is constant, but gravitational potential-energy loss continues to be transferred to thermal stores.
Worked transfer
As a body falls, gravitational potential energy decreases. While weight exceeds drag, kinetic energy increases; increasing drag also transfers more energy thermally. At terminal fall, weight equals drag, so acceleration is zero and kinetic energy is constant, while continuing gravitational potential-energy loss is transferred to thermal stores.
Guided practice
Explain why “At terminal velocity no forces act and no energy is transferred.” fails. Then construct one example that correctly applies air resistance and terminal velocity.
Independent practice
Sketch and explain how weight, drag, acceleration, speed, kinetic energy and gravitational-potential-energy transfer change from release until a falling sphere reaches terminal velocity.
Return to the recorded repair plan when the explanation and application are secure enough to re-test.