# Fluid Dynamics - Hydrostatic Pressure

1. Oct 31, 2015

### Lukas_RSA

1. The problem statement, all variables and given/known data
A rectangular vertical plate is submerged in water. The top edge is horizontal and at a depth of 0.6m. The length of the vertical edge is 1.2m. determine at what dept under the water surface a horizontal line can be drawn on the plate such that the hydrostatic forces on either side of the line is equal. (Hint: The magnitude of the hydrostatic force on a vertical surface is equal to the average pressure x the area.)

2. Relevant equations

3. The attempt at a solution

l1 = 2/3 x 'h
l1 = 2/3 x 1.8
l1 = 1.2

i am not even sure how to draw this question, there is no picture with the question, normally i start off by drawing the problem and adding all the know values,

i hope to hear from you soon.

regards
Lukas van Rooyen

2. Oct 31, 2015

### SteamKing

Staff Emeritus
Well, take it in steps.

1. A rectangular plate is submerged in water.
The surface of the water is located above the top edge of the plate.

2. This plate is vertical.
This means the plate is oriented such that its height is perpendicular to the surface of the water, while its width is parallel to the surface of the water.

3. The length of the vertical edge is 1.2 m.
This plate is 1.2 m tall in the vertical direction, perpendicular to the surface of the water.

4. The top edge is horizontal and at a depth of 0.6 m.
This means the top edge of the plate is 0.6 m below the surface of the water. The top edge is also parallel with the surface of the water.

You should be able to make a sketch of the plate using these four characteristics.

Determine at what depth under the water surface a horizontal line can be drawn on the plate such that the hydrostatic forces on either side of the line are equal. (Hint: The magnitude of the hydrostatic force on a vertical surface is equal to the average pressure x the area.)