If the weight force down is larger than the upward push of the water on the object then the object will sink. If the reverse is true then the object will rise – rising is the opposite of sinking.
Density – The way the molecules are packed in an object that creates the opportunity to float or sink. To put in simple, how tightly the matter/molecules are present in an object.
If the molecules are tightly packed together in an object then the density is greater so the object sinks. Ex: Coin, key, stone…
If the molecules are loosely packed together in an object then the density is lesser so the object floats. Ex: rubber ball, wood, thermocol…
Gravity – It also plays a major role in whether an object will sink or float. For example the ice cube in the water floats, gravity is trying to push the ice-cube down and yet the density of the ice cube is so light that it is pulling it up.
Shape – Shape of an object can also cause float or sink. Put a small ball of clay in the water it will sink, but try again by flattening the clay into the shape of boat or raft it will not sink.
Air – If is an object is filled with air, then it will float. For ex: Life jacket…..
Buoyancy –If an object displaces more water than its actual weight, then it will float. That’s how a massive, steel aircraft carrier can float. Why do we lay on our backs to float on water? That’s to put more surface area against the water, thereby displacing more water than our body weight. This is why we feel so much lighter in water.
Float: to stay on or near the top of a liquid
Sink: to go down below the surface of a liquid
Density: amount of matter in a given amount of space
Molecule: Atom present in an object
Buoyancy: is a force on an object making that object rise or move upward
Gravity: is the force that makes everything fall down towards the earth
Displaced: as the objects drop in the water level rises