buoyant force

Buoyant force is the upward push a liquid gives to an object placed in it.

• This push happens because water presses on all sides of an object, but the pressure is greater deeper down. The stronger push from below creates a net upward force.
• The buoyant force is bigger when an object displaces more water. For example, a large empty plastic bottle pushes aside more water than a small coin, so it receives a stronger upward push.
• A useful way to picture it is holding a beach ball underwater: the water seems to “want” to lift the ball back up. That lifting effect is buoyant force.
• Whether something floats depends on the balance between its weight downward and the buoyant force upward. A floating object has these forces balanced.
• Even very heavy objects, such as ships, can float because their hollow shape displaces a large amount of water. Their overall average density is then less than that of water.