Understanding Object Properties During Water Immersion

When a solid object is immersed in water, several physical quantities are affected. Let's analyze each option:

• Mass: Mass is the amount of matter in an object. It is an intrinsic property and does not change regardless of whether the object is in air or immersed in water.
• Density: Density is defined as mass per unit volume ($\rho = \frac{m}{V}$). The object's own mass and volume do not change upon immersion, so its density remains constant.
• Buoyant Force: According to Archimedes' principle, an immersed object experiences an upward buoyant force equal to the weight of the fluid it displaces ($F_B = \rho_{fluid} \times V_{displaced} \times g$). This force exists *because* the object is immersed; it doesn't decrease.
• Apparent Weight: This is the weight of the object as it seems to be when measured in a fluid. It is calculated as the object's actual weight in air minus the buoyant force acting on it. The formula is:

  $W_{apparent} = W_{actual} - F_B$

  Since the buoyant force ($F_B$) is positive when the object is immersed in water, the apparent weight ($W_{apparent}$) will always be less than the actual weight ($W_{actual}$). Therefore, the apparent weight decreases.

Conclusion on Decreasing Quantity

Based on the analysis, the apparent weight is the quantity that decreases when a solid object is immersed in water due to the upward push from the buoyant force.