Buoyancy and Density: Why Objects Sink or Float

What is the direction of the gravitational force acting on an object?

What is the buoyant force equal to?

According to Archimedes Principle, what happens when the buoyant force is stronger than gravity?

Why does a copper cube sink in water?

What is the relationship between the buoyant force and the gravitational force?

What determines whether an object will sink or float in a fluid?

What is the net result when the buoyant force and gravitational force are equal?

What is the primary reason why objects of the same size, like the wooden and copper cubes, have different buoyant forces acting against gravity?

What happens to an object with a density greater than that of water?

What is the formula for calculating density?

Why do large metal ships float despite being made of dense metal?

What is the result of increasing the surface area or volume of an object without increasing its mass?

Why does the wooden cube float while the copper cube sinks?

What is the condition for an object to float on water?

Why do metals tend to sink in water?

What Determines if an Object Sinks or Floats?

Every object on the planet is subjected to the force of gravity, which pulls it towards the Earth.
When an object is placed in a fluid (like water), the fluid exerts a force on the object in the opposite direction of gravity, known as buoyancy.
Buoyancy is equal to the volume of the fluid displaced by the object.

Archimedes' Principle

Archimedes' Principle states that when an object is placed in a fluid, the fluid will exert a force back on the object that is opposite the direction of gravity.
If the buoyant force is stronger than gravity, the object will float.
If the buoyant force is weaker than gravity, the object will sink.

Relationship between Density and Floating

Density is the measure of the mass of an object in relation to its volume.
If an object has a greater density than the fluid it's placed in, it will sink.
If an object has a lesser density than the fluid it's placed in, it will float.
The density of liquid water is approximately 1 gram per cubic centimeter (g/cm³).

Calculating Density

The formula to calculate density is: density = mass / volume
To calculate the density of an object, divide its mass by its volume.

Examples: Wooden and Copper Cubes

A wooden cube with a mass of 0.45 grams and a volume of 1 cm³ has a density of 0.45 g/cm³, which is less than the density of water, so it floats.
A copper cube with a mass of 8.96 grams and a volume of 1 cm³ has a density of 8.96 g/cm³, which is more than the density of water, so it sinks.

How to Make Something Float

By increasing the volume or surface area of an object, but not its mass, its relative density can be decreased, making it float.
This is how metal ships are able to float, despite being made of dense materials, by spreading out the metal mass over a large area and including air pockets and rooms within the ship.

Understand the concept of buoyancy and density and how they affect whether an object sinks or floats in a liquid. Learn why a wooden cube floats and a copper cube sinks in water.