Calculating Buoyancy

Weight pulls down, buoyancy pushes up. Buoyancy equals the volume of the displaced water divided by the weight of the water per litre. Fresh water: 1 litre, I kg, Sea water, 1 litre, 1.03 kg

[@HolgerDanske89]

at 8:33 in the video you've made a mistake.. 82.4kg - 50kg is 32.4kg not 34.2kg. you've accidentally reversed some numbers just so you're aware.

[@DF-cl5bm]

Thanks for that. It's a simple explanation but one that's often overlooked or ignored. For a diver, the difficult variable in the equation is the volume of the diver together with all of the diver's equipment. One thing that is overlooked by dive instruction videos is exactly this. That volume should be a standard known variable for any diver (with equipment) and could be calculated when a diver does a buoyancy check to find out how much weight is needed for neutral buoyancy. The volume of the diver (with equipment, but minus extra weights) can be calculated once the diver establishes how much extra weight is needed to achieve neutral buoyancy. The total volume of the diver (without the extra weights) can then be found by calculating the volume of the water displaced by the diver wearing the extra weights. If you want to be more accurate, you could allow for the volume of the weights as well. It would go without saying that BCDs need to be fully deflated for this exercise. Many diver training classes tend to overlook this and prefer the trial and error method of determining how much weight the diver needs. I've never come across a scale (to weigh diver + equipment but excluding extra weights) used expressly for this purpose. Realistically, once a diver has established (by trial & error) how much extra weight is needed to achieve neutral buoyancy, it obviates the need to do all of the basic arithmetic, which most people want to avoid (sadly). It would serve to remind the diver that either too many or too few weights are being used and alert them to the fact that there's been a change to their equipment.

[@florianmayer4152]

The first 60 seconds are perfect.

[@julyramos9165]

Very easy to understand thanks..