To achieve buoyancy and float in a standard bathtub, you need to significantly increase the density of the water.
Based on the principle demonstrated by Archimedes, floating occurs when the density of the water exceeds the density of your body. Adding salt is the most effective way to increase water density.
According to one estimate, to achieve sufficient density in a standard bathtub to float, you would need to add around 30kg of salt.
Why Salt Helps You Float
Adding salt to water increases its density. Regular tap water is less dense than the human body (on average), which is why most people sink or partially sink. When enough salt is dissolved, the water becomes denser than your body, allowing you to float more easily, much like in very salty bodies of water such as the Dead Sea.
- Principle: Archimedes' principle states that a body immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the body. To float, this buoyant force must be greater than or equal to your body weight.
- Density: Increasing the water's density means a smaller volume of water can match your weight, providing the necessary upward force for buoyancy.
Achieving true flotation where your body rests comfortably on the surface requires a high concentration of salt. The amount cited, around 30kg, indicates the significant quantity needed to elevate the water's density to this level in a typical home bathtub setting.
