Why does a block of plastic released under water come up to the surface of water?

When a block of plastic is released underwater, it ascends to the surface due to the fundamental principles of buoyancy and density.

Here’s a breakdown of why this happens:

1. Buoyant Force: When an object is submerged in a fluid, it experiences an upward force known as the buoyant force. This force is equal to the weight of the fluid displaced by the object.

2. Density Difference: Plastic typically has a lower density compared to water. Density signifies how much mass is packed into a certain volume. Since the density of plastic is less than that of water, the plastic block is less dense than the water it displaces.

3. Archimedes’ Principle: This principle states that the buoyant force acting on an object is equivalent to the weight of the fluid it displaces. If the buoyant force is greater than the weight of the object, the object will float or rise.

4. Resultant Force: Given that the plastic block is less dense than water, the buoyant force acting on it is greater than its own weight. Consequently, there is an overall upward force, propelling the block upwards through the water until it reaches the water’s surface.

In essence, the block of plastic ascends to the surface because its density is lower than that of water, resulting in a stronger upward buoyant force as per Archimedes’ principle. This disparity in density causes the plastic block to float and rise towards the water’s surface when submerged.