-Ex/ Given: Densities () -Water- 1000 kg/m3 -Iron- 7800 kg/m3 -If you can “deadl

Question

-Ex/ Given: Densities ()

-Water-   1000 kg/m3

-Iron-   7800 kg/m3

-If you can “deadlift” (to waist-high) 100 kg of Iron on dry land, how many kg will it “feel” like if you deadlift from the bottom of a pool filled to your chest with fresh water. What will the “apparent weight” be in newtons.

If you can “deadlift” (to waist-high) 100 kg of Iron on dry land, how many kg will it “feel” like if you deadlift from the bottom of a pool filled to your chest with fresh water. What will the “apparent weight” be in newtons

Explanation / Answer

Here one thing is missing in the problem and this is volume of the iron. This can be determined if the length and width or radius of iron is given.

Howver, I am giving you the hint to determine the apparant weight of iron in fresh water:

Let us consider -

W: actual weight, weight when measured in a vacuum (air is good enough)
B: buoyancy (upward)
N: Normal force from the pool floor (upward)

Now, Force balance:
B + N = W

Solve for N:
N = (W - B)

Origin of buoyancy force:
B = rho_water*V*g

Thus:
N = W - rho_water*V*g = apparant weight of the rod

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