Answer: Weight - Buoyant force (net weight in fluid).
- A Weight - Buoyant force (net weight in fluid)
- B The full weight of the ball measured in air
- C Zero, since the ball is still accelerating at terminal velocity
- D The buoyant force alone, ignoring the ball's actual weight
Correct answer: A. Weight - Buoyant force (net weight in fluid)
Explanation: At terminal velocity, acceleration = 0. Net upward force = 0. Drag + Buoyancy = Weight. So Drag = Weight - Buoyancy (apparent weight in fluid).
Since the same volume of fluid must pass every cross-section per second (continuity), the fluid speeds up where the pipe narrows; Bernoulli's equation then says this faster-moving fluid has lower pressure - the principle behind a venturi meter and an aircraft wing's lift.
Concept context
Pressure, buoyancy, Bernoulli equation, viscosity, and surface tension.