I do not know for sure but this is what Chat GBT said (clearly I couent say the true reason but you will get what math neads to be done, and I would add more to be safe)
To determine how much additional weight you need to sink yourself for scuba diving, we need to account for your body's buoyancy. Here's a general approach:
- Calculate your body's volume: Since the human body is approximately as dense as water, you can estimate your volume by dividing your weight by the density of water (approximately 1000 kg/m³).
- Determine the buoyant force: The buoyant force is equal to the weight of the water displaced by your body.
- Calculate the weight needed to counteract the buoyant force: This will be the additional weight you need to wear to sink.
Assuming you weigh 55 kg:
- Volume of your body:V=mρwater=55 kg1000 kg/m3=0.055 m3V = \frac{m}{\rho_{water}} = \frac{55\, \text{kg}}{1000\, \text{kg/m}^3} = 0.055\, \text{m}^3V=ρwaterm=1000kg/m355kg=0.055m3
- Buoyant force:Fb=ρwater⋅V⋅g=1000 kg/m3⋅0.055 m3⋅9.81 m/s2=539.55 NF_b = \rho_{water} \cdot V \cdot g = 1000\, \text{kg/m}^3 \cdot 0.055\, \text{m}^3 \cdot 9.81\, \text{m/s}^2 = 539.55\, \text{N}Fb=ρwater⋅V⋅g=1000kg/m3⋅0.055m3⋅9.81m/s2=539.55N
- Your weight in Newtons:Wyou=m⋅g=55 kg⋅9.81 m/s2=539.55 NW_{you} = m \cdot g = 55\, \text{kg} \cdot 9.81\, \text{m/s}^2 = 539.55\, \text{N}Wyou=m⋅g=55kg⋅9.81m/s2=539.55N
Since the buoyant force equals your weight, you are neutrally buoyant in fresh water. To sink, you'll need to add enough weight to overcome this neutral buoyancy.
Scuba divers typically use lead weights to achieve negative buoyancy. The amount of weight required can vary based on factors such as body composition, wetsuit thickness, and water salinity (saltwater is denser than freshwater). For freshwater, a general guideline is to add about 5-10% of your body weight:
Weight to add=55 kg×0.05 to 0.1=2.75 to 5.5 kg\text{Weight to add} = 55\, \text{kg} \times 0.05 \text{ to } 0.1 = 2.75 \text{ to } 5.5\, \text{kg}Weight to add=55kg×0.05 to 0.1=2.75 to 5.5kg
So, you would need approximately 2.75 to 5.5 kg of additional weight to sink yourself for scuba diving in freshwater. In saltwater, you might need slightly more weight due to its higher density.
