Why can a hollow steel boat float while a solid metal coin sinks?
Show answer & explanation
Answer: The hollow hull displaces enough water to balance the boat’s weight
Water cannot exert any upward force on a small metal coin — A submerged coin does experience an upward buoyant force. It sinks because that force is smaller than its weight, not because small objects receive no buoyancy.
The hollow hull displaces enough water to balance the boat’s weight ✓ — A hollow hull displaces enough water for the upward buoyant force to balance the boat’s weight before it floods. A stationary floating boat displaces water equal to its own weight, not more. A solid coin displaces too little water to balance its weight even when fully submerged.
Water’s surface skin carries the boat’s weight like a stretched sheet — Surface tension does not support the weight of an ordinary steel boat. It can support tiny objects such as a carefully placed needle, but a boat is supported by the pressure forces of the water it displaces.
More Physics in Daily Life questions
- In a warm office that already reads 26 C, which change can make people feel cooler without lowering the thermostat?
- Why might 26 C feel acceptable in a breezy naturally ventilated summer building but too warm in a sealed winter office?
- On a warm, humid day, why can a 27 °C room feel worse once your skin is sweaty?
- Why can moving air make a 27 C room feel cooler without changing the thermometer?
- Why can a desk beside a cold window feel chilly even when the thermostat across the room still reads 22 C?
- Why might someone who just climbed stairs feel warm in a 22 C room while someone sitting in a T-shirt feels chilly?