# Horizontal force across a partition

## Homework Statement

Find the horizontal force across the partition in a water tank with two compartments, one filled with water to x height and the other with water to y height. I've worked out the thrust acting on the partition as a result of density, height, gravity and average depth, so I have two horizontal vectors, with which to find the total horizontal force.

F=PaA
P=pgh
F=pgha

## The Attempt at a Solution

(sum) Fx=(Force from oil) - (Force from water). Problem is I don't know which force is in which direction relative to the partition. The only solution I can see, which would make sense is adding the two forces together. Is this correct?

Simon Bridge
Homework Helper
I'm confused.
You write,
(sum) Fx=(Force from oil) - (Force from water).
... but "oil" is not mentioned in the problem statement, which says:
... two compartments, one filled with water to x height and the other with water to y height.
... just water on each side of the partition.

Looking at those heights:
Lets say y>x, then what else is in the tank at height h: y-x<h<y? What about when h>y?

Problem is I don't know which force is in which direction relative to the partition.
... but your problem statement says:
Find the horizontal force across the partition
... which direction is "horizontal"?

The question says there is a tank which has a vertical partition across the width. There are two compartments in the tank, one contains water the other oil. I have worked out the hydrostatic force each liquid exerts on the partition. Now I have to find the 'horizontal force on the partition', Do I add the two forces together?

I'm confused.
You write, ... but "oil" is not mentioned in the problem statement, which says: ... just water on each side of the partition.

Looking at those heights:
Lets say y>x, then what else is in the tank at height h: y-x<h<y? What about when h>y?

... but your problem statement says: ... which direction is "horizontal"?

Horizontal parallel to the base of the tank, normal to the vertical partition, I assume.

Does the horizontal resultant force equal the difference between the two opposing forces?

Simon Bridge