Imagine you are in a swimming pool 30m deep. Assuming you know that water is denser than air, you would know that the 30m of water above you will carry more weight, and press down on your body. Say you were in a swimming pool 60m deep, you would be sandwiched between 30m of water pressing down on you, and the upthrust created by the 30m of water below you.
In a building 30m up, the pressure will be regulated, as you are in a building. The floor will be strong enough to support the weight of the body, and the body will not recoil into itself.
So,
GPE (graviational potential energy) = mass x g x height
GPE is depends on where zero height is defined. In this situation, we define h = 0 as the initial height.



The builder has gained 18.375 kJ of PE.
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ooh thanks but don't give me advise
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Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: i.e. the components of the mixture have different specific materials and Magnetic separations take advantages of natural magnetic properties between minerals in feed. The separation is between economic ore constituents, noneconomic contaminants and gangue. and saw dust can be separated by gravity separation method. The process can be used for separating insoluble substances which are heavier than liquid by allowing them to settle down on their own due to gravity. The mixture of sand and iron can be separated from each other by using a magnet. Iron gets attracted towards a magnet leaving behind the sand.
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