Question 3
Why does an object float or sink when placed on the surface of water?
Archimedes' principle states that the upward buoyant force exerted on a body, partially or fully immersed in a fluid, is equal to the weight of the fluid displaced.
An object floats in water if it displaces water equal to its weight. In this case, the weight of the body is balanced by buoyant force.
However, if it can't displace water equal to its weight, the buoyant force is less than the weight of the body and it sinks.