Why is the pressure different at points X and Y?

[Taniaz]

Homework Statement

a)Consider the vessel in the figure shown. It contains a liquid of density p. Calculate the pressure, and give the direction of the force on the container due to the liquid, acting at each of the following points.

b) Consider the second figure shown. Why is the pressure the same at point C and D?
Why is the pressure at point X and Y different?

Homework Equations

P=pgh

The Attempt at a Solution

a) I'm not sure what the pressure is at point B. Sometimes I think the pressure is 0 but sometimes I think the pressure is P=pg(h1-h2) because the pressure is the same at all points on a horizontal plane.

b) The pressure at C and D is the same because they're at the same horizontal level.
The pressure at X and Y is different because they lie in different liquids (oil and water) so the density is different therefore the pressure is different?

 

[Doc Al]

but sometimes I think the pressure is P=pg(h1-h2) because the pressure is the same at all points on a horizontal plane.

Sometimes you are correct. ;)

The pressure at X and Y is different because they lie in different liquids (oil and water) so the density is different therefore the pressure is different?

Correct.

In the same fluid at the same height, the pressure must be the same.

 

[Taniaz]

Thank you!