Science Models
Science Fair Projects

Published on May 25, 2017

Water Pressure vs Buoyancy


The objective: To determine whether water pressure affects the buoyancy of selected objects


Why won't this plastic ball float? Is it because the object is not buoyant, or is it because the water pressure level is too high? I'll go find out the reason right now.

In my experiment, I got two straws. I sealed one straw with a lump of clay at both ends, and a ballast in the middle. I sealed the other straw with a lump of clay at only one end. Then, I put both straws in a 1-liter bottle, and tested the narrow diameter of it at the current point, and after every 0.5 inches. I started that from ten, and took off the measurement until it got to 0. While I was doing the experiment, I took pictures and graphed the results in charts, and took pictures to record my observations.

In science, buoyancy is an upward force exerted, (or pushed out); buy a fluid that opposes the weight of an immersed object. In an easier way to say it: a type of force that is pushed out by a fluid or liquid that goes against the weight of a plunged object, or being able to float.

Water pressure is the force that pushes water through pipes, or any other objects, and determines the flow of water from the tap. Low pressure can reduce water flow, and high pressure can increase leakage and the number of repairs we undertake on pipes. These definitions are used in examples.

Water pressure and buoyancy can also depend on other things as well, such as density, density particles, forces, etc.

With too much pressure, the floating object will become less buoyant and start to become unstable, therefore beginning to sink. Different levels of water pressure affect buoyancy because water pressure weakens and hurts living things, (such as humans), so they are no longer able to stay afloat, and sinks nonliving, un-buoyant, and even buoyant objects if it is to great or high. The reason why this happens is because when too much pressure is applied, the object that helps in being a ballast can no longer hold the object because the pressure can either, shrink, crush, or weaken it; and as you know, causing it to sink.

Some things that can cause low water pressure are: Pressure regulators, Elevation, Home valves, Water leaks, Peak periods, Mineral deposition.

All of those things are the cause of low water pressure is because low pressure can reduce water flow, so when those changes happen, the water pressure is reduced, causing low pressure. Like I stated earlier, low pressure is not the best thing in the world because it can reduce water pressure.

Water pressure is a little bit different. High pressure can be caused by the recent maintenance work done to the house, (or any place), or the particular area your are in.

It is important to know these facts about high pressure, low pressure, etc, because any of it can cause damage to the area it is in, or help it improve in that level. This has a use in real life situations because you can learn what's good and bad in the water pressure in pipes and other resources.

So now I know that water pressure does affect buoyancy. The reason to sum it up is because it can damage and affect the ballast and object, causing it to tip over and become really unstable. Then eventually the object can not take the pressure anymore, and it, therefore, sinks.


To see if different levels of capacity and water pressure affect the buoyancy of an object when altered


I think that different levels of water pressure will affect buoyancy in both straws because it will go past their capacity.


• One-liter transparent bottle

• 2 transparent drinking straws

• Modeling clay

• 1 tall drinking glass

• Water


1. Cut a 4-inch length of straw and seal one end with a lump of clay . That will be the top of the straw. Attach a ring of clay to the straw near the end to serve as the ballast to keep it upright. Adjust it so that it floats in a stable manner.

2. Repeat this process with the second straw, but seal this one with clay at both ends. Check the seals of both straws.

3. Fill the bottle with water to within 1-2 inches of the neck. Carefully place the two straws in the bottle with the bottom end of the straws down. Close the bottle and make sure it is sealed tightly.

4. Position the bottle on a counter so that one person can squeeze the bottle while the other writes down the measurements with a ruler of the change of the bottles width when it is squeezed. The measurement will serve as a rough gauge of the pressure applied to the water and objects inside the bottle.

5. Measure and record the diameter of the bottle. Gently squeeze the bottle until its width has decreased by 0.5 inch. Record any change that occurs with the straws, (ex. Sinking, taking on water, deforming, etc.) in the appropriate column on your data chart. Repeat this process for each 0.5 inch change in the bottle's width.

6. Continue squeezing until the second straw sinks or until no more pressure can be applied safely to the bottle.

7. When the pressure is released, the straw or straws should regain their buoyancy and return to the surface. Then note the changes and watch for rising in the unsealed straw and deformity of the second straw. Test which flattens as the pressure is increased.

8. Examine your results and determine whether your hypothesis is true.


The first straw was affected because one end was not sealed with clay. The water climbed up the straw when the bottle was squeezed. Therefore, the clay ballast could no longer hold the pressure, causing the straw to sink.

Water Pressure


After doing my experiment, I found out that my hypothesis was wrong and right. I thought that both straws would get affected by the water pressure that was applied. The reason why I was wrong was because Straw 2 (with closed ends) was not affected; only Straw 1 (with open ends) was. My experiment did end up well. What was supposed to happen happened, and my hypothesis was somewhat correct.










Science Fair Project done By Jessica Lim