Why do objects with higher density than water sink?

Objects with higher density than water sink because they are heavier per unit of volume than the water they displace.

In more detail, this phenomenon is explained by Archimedes' Principle, a fundamental concept in fluid mechanics. Archimedes' Principle states that the buoyant force (or upthrust) on an object submerged in a fluid is equal to the weight of the fluid displaced by the object. The buoyant force is the force exerted on an object that is wholly or partly immersed in a fluid, pushing it upwards.

If an object is denser than the fluid it is in, it will displace less fluid than its own weight, resulting in a smaller buoyant force than the weight of the object. This imbalance of forces causes the object to sink. On the other hand, if an object is less dense than the fluid, it will displace more fluid than its own weight, resulting in a larger buoyant force than the weight of the object. This causes the object to float.

Density is defined as mass per unit volume. If an object has a higher density than water, it means that a given volume of the object weighs more than the same volume of water. When such an object is placed in water, it displaces an amount of water equal to its own volume. However, because the object is denser, it weighs more than the water it displaces. The buoyant force exerted by the water, which is equal to the weight of the displaced water, is therefore less than the weight of the object. This results in a net downward force, causing the object to sink.

In summary, whether an object sinks or floats in water is determined by its density relative to water. Objects denser than water sink because the buoyant force exerted by the water is less than the weight of the object.