Answer: minimise its surface area.
- A minimise its surface area
- B maximise its surface area
- C increase its volume
- D lower its density
Correct answer: A. minimise its surface area
Explanation: A sphere has the least surface area for a given volume, minimising surface energy.
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.