When you drop a coin in a glass of water, it sinks, but when you place a bigger wooden block in water, it floats. Explain.
When an object is placed in water, two forces act on it: the gravitational force pulling it downward and the buoyant force pushing it upward.
A coin sinks because its weight (gravitational force) is greater than the buoyant force exerted by water on it.
A wooden block floats because the buoyant force equals its weight.
According to Archimedes' Principle, an object floats when the weight of water displaced equals the object's weight, and sinks when its weight is greater than the weight of water displaced.
Explanation
The chapter explains that 'If the gravitational force is more than the buoyant force, the object sinks, but if the two forces are equal, the object floats.' Archimedes' Principle is also discussed: 'If the weight of a liquid displaced by an object is smaller than the weight of the object, the object will sink in the liquid.'
Solution Steps
Two forces act on objects in water: gravitational force (downward) and buoyant force (upward)
A coin sinks because its gravitational force is greater than the buoyant force
A wooden block floats because buoyant force equals its weight
Archimedes' Principle: object floats when displaced water weight equals object weight, sinks when object weight is greater