A) it is easier to lift up a load in water than in air, why?

Short

buoyancy

Long

    An object submerged in water displaces water according to how much it weighs. In fact, the water will push upward against the object with a force equal to the weight of the water it displaces. For example, a bowling ball and a beach ball that are the same size will have the same volume. The bowling ball, however, is more massive and thus denser than the beach ball. In both cases, the water pushes up against the ball with a force equal to the weight of water it displaced. In the case of the bowling ball, it weighs more than the amount of water it displaced, so it sinks. The beach ball, however, displaces very little water and the air inside it is much lighter than the weight of the water it displaced, so it floats.When lifting something underwater, you have the help of water pushing the object upwards along with your own strength, which is why it's easier to pick up things underwater than on land.

Source:

https://www.wonderopolis.org/wonder/why-is-it-easier-to-lift-someone-in-water-than-on-land

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