1.27

Approximate calculation
1. Assume a filled bathtub holds about 150 L (=150 000 mL).
2. A typical drinking straw has an inner diameter ≈ 5 mm ⇒ cross-sectional area A = π·(2.5 mm)² ≈ 19.6 mm² = 1.96 × 10^-5 m².
3. Strong, sustained suction can pull water through the straw at roughly v ≈ 0.30 m/s.
4. Volumetric flow rate Q = A·v = 1.96 × 10^-5 m² · 0.30 m/s ≈ 5.9 × 10^-6 m³/s = 5.9 mL/s.
5. Time required T = volume / rate = 150 000 mL / 5.9 mL s^-1 ≈ 25 400 s ≈ 7 h.

Result: Even with continuous, vigorous sucking you would need roughly 7–8 hours to empty a standard bathtub with a single drinking straw (and real people would tire long before finishing).

Return to Chapter 1 .