Correct Answer to Question 2

The starting point is this: the pressure at level X must be the same on both sides of the U-tube. If that were not so, the water in the bottom of the U would be accelerating - and it isn't.

On the left side, the pressure at X is the atmospheric pressure P₀ plus the pressure due to a column of oil H_oil = 35 cm high. This last pressure is _oilgH_oil.

On the right, the pressure at X is again the atmospheric pressure P₀ plus _WgH_W, where the subscripts W stand for water. So,

P₀ + _oil * g * H_oil = P₀ + _W * g * H_W

or

_oil * H_oil = _W * H_W

and

H_W = (_oil/_W) * H_oil = (0.8*10³/1*10³) * 0.35 = 0.28 m = 28 cm.

Formula Sheet

Question 2

Question 3

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