Introduction: (Initial Observation)
All egg packages are designed to hold the egg in a vertical position. Is there any special reason for this form of packaging? Do eggs withstand a greater force from one direction than from others? I have also seen many dome shaped roofs that look like the top or bottom of an egg. Are dome shaped roofs stronger than flat roofs? Is it possible that the idea of a dome shaped roof actually came from the egg?
This is an experimental project in physics. You will use scientific method to complete your project.
Significance: Egg producers need to know the strength of the egg in different directions in order to design a new egg packaging. Proper positioning of the egg can reduce the rate of breakage.
Find out about what you want to investigate. Read books, magazines or ask professionals who might know in order to learn about the effect or area of study. Keep track of where you got your information from.
You might have many different reasons for studying the strength of an egg.
An engineer who designs roofs, doorways and bridges, may be interested in the strength of arch designs in order to use it in his/her future designs and calculations.
A packaging specialist may need to know the strength of an egg from different directions, in order to design a new package for the storage and shipping of those eggs.
An egg producing farmer may be studying animal feeding habits that contribute to the strength of egg shells. Such farmers may feed different groups of birds with different types of foods in order to see which specific foods cause production of strong egg shells.
While gathering information, do not try to find experiment results. Someone may have published his/her test results of the strength of a certain egg; however, such results are not useable for you. Following is a guideline on gathering relevant information:
- Gather information about different types of strength (Tensile, compressive,…)
- Gather information about methods and equipment of measuring strength.
- Find out about packaging and egg packaging methods, designs and material.
- Study arch design and its uses.
Can the above information be used as my Background information?
Background information are usually the information that raise questions and make you think of a project. A sample of background information is shown in the introduction section of this project guide. You can add additional, relevant, information that you gather to your background information.
Tensile strength is the resistance of a material to a force tending to tear it apart, measured as the maximum tension the material can withstand without tearing. Tensile strength is important for material that are pulled such as ropes, belts, strings, chains.
Compressive strength is the maximum compression a material can withstand without failure. Compressive strength is important for stone, concrete, bricks, asphalt, and other construction material that are being compressed under heavy loads.
Need background information? Simply combine the introduction section and the gathering information section and then make a summary of that.
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement. This is a sample:
While designing a new egg crate, we are wondering what would be the best orientation for the egg for maximum strength. Not paying attention to the physical strength or weakness of an egg from different directions may cause the design of a crate that is not able to protect fragile eggs. This would then increase the rate of breakage and loss. A more specific question is:
Can eggs withstand a greater force from some directions than from others?
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
The Independent Variable (also known as manipulated variable) is the orientation of the egg (upright, on the side).
The Dependent Variable (also known as responding variable) is the maximum force that an egg withstands prior to breaking.
Constants are the source, type and size of the egg as well as the method, procedures and test instruments.
Controlled variables are temperature, sounds and other environmental conditions that may contribute to breakage of the egg.
Based on your gathered information, make an educated guess about what types of things affect the system with which you are working. Identifying variables is necessary before you can make a hypothesis.
Following is a sample hypothesis:
The arch form is being used in many structures such as bridges to provide strength. Eggs have an arch design from every direction; however, the arch is more curved when the egg is placed upright, therefore it is expected to have a higher strength when it is placed upright.
You may come up with your own hypothesis. Hypothesis does not have to be correct. Your experiments will later support or reject your hypothesis.
Another format for stating your hypothesis:
If I change the orientation of the egg from horizontal to vertical, then the strength of the egg will increase.
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.
Test the compressive strength of eggs in different orientations.
Introduction: To test the strength of the egg in different orientations, we need to assemble a device, allowing us to apply a variable amount of force in a controlled direction.
One of the ways to do this is assembling a few pieces of wood like a clamp. We do this so that the pressure to the egg will be at a controlled direction.
Use pieces of wood to assemble a device like a clamp. Secure the egg between the jaws of the clamp in the position that you want to test. Place an empty plastic container right above the egg on the upper jaw of the clamp.
Start adding water to the plastic container until the egg breaks.
Repeat this experiment 3 times for each of two directions and record the results.
For the best results you should make your device adjustable to the height of the egg in either the vertical or horizontal position. In this way, in both tests, the upper and lower jaws will be in a horizontal position.
For the jaws of this clamp, you may use two pieces of 1×4 pine wood, about 2.5 feet long each. Use a plastic container that holds one gallon or more.
Make sure the jaws are almost parallel to each other with egg in place. Lift the upper jaw, place the egg in position and then slowly lower the upper jaw to hold the egg. If the jaws are parallel to each other, two jaws should be able to hold the egg in place.
I used two smaller pieces of wood to keep the jaws apart. Both pieces were used while testing the egg in vertical position, but later I removed one to adjust the opening for the egg in the side way.
First experiment smashed the egg and made a mess. Therefore, for the rest of my experiments, I placed another piece of wood next to the egg. This piece was slightly shorter than the egg, so it was not affecting our test results, but this time when the egg broke, the upper jaw could not come down to smash the egg.
Your data table will contain the force (weight) it took to break the egg in each orientation. See samples of data tables in the results section below.
Materials and Equipment:
A few pieces of wood to assemble a clamp.
Bucket or plastic container.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. In the egg experiment, response is sudden (when the egg brakes). So what you record is the amount of weight that brakes the egg in each test.
Your results table will look like this:
Compressive strength of egg while placed upright:
Compressive strength of egg while placed on the side:
You may combine the results in a table like this:
|Egg orientation||Egg strength|
|on the side|
Use your results table to draw a bar graph or bar chart. You will have two bars. Each bar represents a different orientation of the egg. The height of the bar will represent the strength of the egg in each orientation.
You may write the orientation and the strength on each bar or on the side.
Since the upper jaw, empty plastic container and water that you add later all have different weights, you will need to calculate the total weight that brakes the egg.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. By studying tables and graphs, we can see trends that tell us how different variables determine our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
In your conclusion, you may also have statements like this:
The shell material is better suited to compression than bending. With a load along the longitudinal axis of the egg, the bending stresses are less than the compressive stresses and vice versa.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
You may find books related to Material Strength (or Strength of Material) and use them as a reference for this project. Such books can be found in the physics or Mechanics section of libraries.