Explain how the small amount of water inside the column formed by the sandbags is able to balance the much larger body of water behind the levee.
Figure 4. Because the river level is very high, it has started to leak under the levee. Sandbags are placed around the leak, and the water held by them rises until it is the same level as the river, at which point the water there stops rising.
Does atmospheric pressure add to the gas pressure in a rigid tank? In a toy balloon? When, in general, does atmospheric pressure not affect the total pressure in a fluid?
You can break a strong wine bottle by pounding a cork into it with your fist, but the cork must press directly against the liquid filling the bottle—there can be no air between the cork and liquid. Explain why the bottle breaks, and why it will not if there is air between the cork and liquid. The greatest ocean depths on the Earth are found in the Marianas Trench near the Philippines. Calculate the pressure due to the ocean at the bottom of this trench, given its depth is Water towers store water above the level of consumers for times of heavy use, eliminating the need for high-speed pumps.
How high above a user must the water level be to create a gauge pressure of 3. How much force is exerted on one side of an 8. How can the paper withstand such a force?
What pressure is exerted on the bottom of a 0. The left side of the heart creates a pressure of mm Hg by exerting a force directly on the blood over an effective area of What force does it exert to accomplish this? Show that the total force on a rectangular dam due to the water behind it increases with the square of the water depth. You may assume the face of the dam is vertical. Hint: Calculate the average pressure exerted and multiply this by the area in contact with the water.
See Figure 5. Skip to main content. Fluid Statics. Search for:. Variation of Pressure with Depth in a Fluid Learning Objectives By the end of this section, you will be able to: Define pressure in terms of weight. Explain the variation of pressure with depth in a fluid.
Calculate density given pressure and altitude. Example 1. Table 1. Water, like all things on Earth, is pulled downward by the force of gravity. Every body of water has a certain weight, and this weight pushes downward on whatever is below it. Water pressure is the result of the weight of all the water above pushing down on the water below.
As you go deeper into a body of water, there is more water above, and therefore a greater weight pushing down. This is the reason water pressure increases with depth. The pressure depends only upon the depth, and is the same anywhere at a given depth and in every direction.
Pressure is measured in units of force such as pounds, lb. Other ways of measuring pressure are also common. An often convenient unit is the atmosphere, atm, equal to the pressure of the atmosphere at sea level.
Traditionally, pressure is measured using a barometer, a device in which a column of liquid mercury, typically is pushed up by the air pressure outside.
The calculation of water pressure is very straightforward. Imagine a flat surface at the depth for which you want to calculate the pressure.
All you have to do is find the weight of all the water on top of that surface, then divide it by the area of the surface. The pressure in a liquid is different at different depths. Pressure increases as the depth increases. The pressure in a liquid is due to the weight of the column of water above. Since the particles in a liquid are tightly packed, this pressure acts in all directions.
For example, the pressure acting on a dam at the bottom of a reservoir is greater than the pressure acting near the top. This is why dam walls are usually wedge-shaped. The pressure caused by a column of liquid can be calculated using the equation:.
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