# Buoyancy

A 50kg block of concrete is being raised from a lake. What fraction of its weight in air is required to lift it while submerged?

My attempt,

I’m pretty sure this question pertains to Archimedes principle

I calculated the weight of the block (force due to gravity) and noted that the buoyancy force is equal to the weight of fluid displaced

Buoyancy = ρgV = ρgAy

And this is where it hit the buffers I’m not so sure how to proceed?

I think that it would be something like, calculate the buoyancy force and the force which would be needed to lift the block (in air) and then subtract the two as the buoyancy force would aid the elevation and then take some kind of ratio of that mass required and the given mass?

Any help would be great I think I have given enough information:)

Thanks for any help in advanced:)

Regards

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