A cylindrical disk of wood weighing 45.0 N and having a diameter of 30.0 cm floats on a cylinder of oil of density 0.850 g/cm3 (?Fig. E12.21?). The cylinder of oil is 75.0 cm deep and has a diameter the same as that of the wood. (a) What is the gauge pressure at the top of the oil column? (b) Suppose now that someone puts a weight of 83.0 N on top of the wood, but no oil seeps around the edge of the wood. What is the ?change in pressure at (i) the bottom of the oil and (ii) halfway down in the oil?
Solution 21E Step 1 of 4: a) The gauge pressure at the top of the oil column w p p0= A = w2 r 45 N = 0.0707 m = 636 Pa Step 2 of 4: b)The increase in pressure produces a force on the disk equal to the increase in weight. By Pascal’s law the increase in pressure is transmitted to all points in the oil.