Introduction: (Initial Observation)
We live in the machine age and depend on machines for almost every activity of our daily lives. A machine is a tool used to make work easier. Simple machines are simple tools, with no moving parts, used to make work easier. Compound machines have two or more simple machines working together.
Machines do not increase the amount of work done, but they do make work easier. Machines make work easier by changing force or distance, or by changing the direction of the force.
Many tasks, such as lifting heavy objects, are practically impossible without machines. In this project you will design and construct a machine that can lift a heavy object with a force less than the weight of the object.
Parent support and supervision is required for this project.
Information Gathering:
Find information on simple machines and compound machines. Read books, magazines or ask professionals who might know in order to learn how machines can make the work easier. Keep track of where you got your information from.
Question/ Purpose:
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.
The purpose of this project is to design and construct a machine that can lift a heavy object with a relatively small force.
One specific question is:
How does the location of pivot point in relation to load and effort affect the amount of force needed to lift certain weight.
Identify Variables:
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.
Manipulated variable is the location of pivot point.
Responding variable is the effort force required to lift a certain weight.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. This is a sample hypothesis:
As the pivot point gets closer to the load, we will need less effort to lift it.
Experiment Design:
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.”
Experiment 1: Lift a heavy object.
Introduction: A lever is a simple machine that can lift a heavy object. The only problem is that a lever needs to tilt to one side or the other. Tilting is a potential problem and may cause an object to fall. In this project you will construct a dual beam lever in order to keep the objects horizontal. This is very similar to a dual beam balance. The only difference is that the one side is longer than the other. In this way you can use a smaller force to lift a heavier object.
Procedure:
You can use wood moldings with a rectangular cross section to construct most of the parts for your project. In the images shown below we have used wood sticks with a thickness of 1/4″ and a width of about 1″. You may use any similar size with the same results.
We have also used 3/8″ wood dowels as joints; however, you may use any other size dowels or nails.
Cut 2 sticks of 14″ long each.- Measure exactly one inch from each end of each stick and make a hole slightly larger than your wood dowels. These holes will carry the loads.
- Make another hole 5 inches from one side of each stick (it will be 9 inches from the other side). These holes will be pivot points.
Cut another stick of wood 7 inches long that will hold the pivot points. Make two holes, one exactly one inch from the edge and the other 3 inches from the same edge. These holes will be exactly 2″ apart. In each hole insert a 1″ long wood dowel and use wood glue to secure it.- Cut two 6″ long pieces to hold the loads. Make two holes in each of the pieces, one exactly one inch from the edge and the other 3 inches from the same edge.
- In each hole insert a 1″ long wood dowel and use wood glue to secure it. Glue a 3″ x 3″ piece of wood on the end that is away from the wood dowels.
In our model we have made some extra holes. You can ignore them.
- Use a flat board as the base. Attach a few wood blocks to the center of board to form a secure base for your pivot stick.
Connect the pieces to each other as shown in the picture in the right. You may need to sand the wood dowels or enlarge the holes so the beams can swing freely.- Put a 500 gram weight on the side that is closer to pivot points. A smaller load on the other side will be able to lift this load.
Additional Experiments:
As you see, we have made additional holes on the beams. Holes are 2 inches apart from center to center. These holes can help us to change the pivot point to see how the location of pivot point affect the force needed to lift a load. If you are doing this experiment, you may write your experiment results in a table like this:
| Resistance Arm Distance from load to the pivot point |
Effort Arm Distance from effort force to the pivot point |
Effort force |
| 2″ (2 inches) | 10″ | |
| 4″ | 8″ | |
| 6″ | 6″ | |
| 8″ | 4″ | |
| 10″ | 2″ |
Using Pulleys
You may also construct a lifting device with similar ability using pulleys.
To do this, you will need a wooden frame that can be used to hang the pulleys. A smaller frame or box can be used to hold the weight. Try this only if you can find small pulleys in your local hardware store.
Connect one end of the string to the upper bar of the frame. Pass the other end through the pulley of the lifting box, and then through one or two upper pulleys; finally connect this end to another box or metal can.
In this model 250 grams mass in the can will balance with 500 grams load in the box. Any mass in excess of 250 grams in the can will lift the 500-gram load.
Another sample:
The picture on the right shows a similar model that uses a wood dowel and a handle like a wheel to pull the string down. With this method you can lift a much heavier weight with very little effort.
Materials and Equipment:
List of material may vary depending on your final experiment design.
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. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Calculations:
Write your calculations (if any) in this section of your report.
Summery 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. Studying tables and graphs, we can see trends that tell us how different variables cause 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.
Conclusion:
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.
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.
Possible Errors:
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.
References:
List of References
