Buoyancy - Sinking Boat


To illustrate buoyancy in a perhaps counterinutuitive way.


Fish tank with copper boat.

Setup Time

5 min.




    A heavy copper "boat" floats in a fish tank "pond." A cork is removed from a hole in the bottom of the boat, allowing the boat to fill with water and sink. Q: When the boat sinks, will the water level in the pond (a) go up, (b) go down, or (c) remain the same? A: As the boat sinks, the water level in the pond goes down.◙


    George M. Koehl, Archimedes' Principle and the Hydrostatic Paradox - Simple Demonstrations, AJP 17, 579-580 (1949). ◙G. M. Koehl, Simple demonstration experiments, Proceedings of the AAPT, AJP 17, 231-232 (1949). ◙Meiners, Physics Demonstration Experiments, Section 16-2.5 and 16-2.6, pp. 378-379.