Simple Machines

Introduction: (Initial Observation)

Can you open a screw without screw driver? Or cut a string without scissors? It might be possible but it is very hard. That is why we use different machines in our daily life. A machine is a tool used to make work easier. Simple machines are simple tools used to make work easier. Compound machines have two or more simple machines working together to make work easier.

In this project you will design and perform experiments to demonstrate how do different machines make work easier.

Information Gathering:

Find out about simple machines. Read books, magazines or ask professionals who might know in order to learn about the usage of each simple machine in our daily life or in other compound machines. Keep track of where you got your information from.

In science, work is defined as a force acting on an object to move it across a distance. Pushing, pulling, and lifting are common forms of work. Furniture movers do work when they move boxes. Gardeners do work when they pull weeds. Children do work when they go up and down on a see-saw. Machines make their work easier. The furniture movers use a ramp to slide boxes into a truck. The gardeners use a hand shovel to help break through the weeds. The children use a see-saw to go up and down. The ramp, the shovel, and the see-saw are simple machines.

Inclined Plane
A plane is a flat surface. For example, a smooth board is a plane. Now, if the plane is lying flat on the ground, it isn’t likely to help you do work. However, when that plane is inclined, or slanted, it can help you move objects across distances. And, that’s work! A common inclined plane is a ramp. Lifting a heavy box onto a loading dock is much easier if you slide the box up a ramp–a simple machine. Want to know more? Here’s extra information.

Wedge
Instead of using the smooth side of the inclined plane, you can also use the pointed edges to do other kinds of work. For example, you can use the edge to push things apart. Then, the inclined plane is a wedge. So, a wedge is actually a kind of inclined plane. An axeblade is a wedge. Think of the edge of the blade. It’s the edge of a smooth slanted surface. That’s a wedge! Want to know more? Here’s extra information.

Screw
Now, take an inclined plane and wrap it around a cylinder. Its sharp edge becomes another simple tool: the screw. Put a metal screw beside a ramp and it’s kind of hard to see the similarities, but the screw is actually just another kind of inclined plane. Try this demonstration to help you visualize. How does the screw help you do work? Every turn of a metal screw helps you move a piece of metal through a wooden space. And, that’s how we build things! Want to know more? Here’s extra information

Lever
Try pulling a really stubborn weed out of the ground. You know, a deep, persistent weed that seems to have taken over your flowerbed. Using just your bare hands, it might be difficult or even painful. With a tool, like a hand shovel, however, you should win the battle. Any tool that pries something loose is a lever. A lever is an arm that “pivots” (or turns) against a “fulcrum” (or point). Think of the claw end of a hammer that you use to pry nails loose. It’s a lever. It’s a curved arm that rests against a point on a surface. As you rotate the curved arm, it pries the nail loose from the surface. And that’s hard work!

Wheel and Axle
The rotation of the lever against a point pries objects loose. That rotation motion can also do other kinds of work. Another kind of lever, the wheel and axle, moves objects across distances. The wheel, the round end, turns the axle, the cylindrical post, causing movement. On a wagon, for example, the bucket rests on top of the axle. As the wheel rotates the axle, the wagon moves. Now, place your pet dog in the bucket, and you can easily move him around the yard. On a truck, for example, the cargo hold rests on top of several axles. As the wheels rotate the axles, the truck moves. You can move your dog across the country! Want to know more? Here’s extra information.

Pulley
Instead of an axle, the wheel could also rotate a rope or cord. This variation of the wheel and axle is the pulley. In a pulley, a cord wraps around a wheel. As the wheel rotates, the cord moves in either direction. Now, attach a hook to the cord, and you can use the wheel’s rotation to raise and lower objects. On a flagpole, for example, a rope is attached to a pulley. On the rope, there are usually two hooks. The cord rotates around the pulley and lowers the hooks where you can attach the flag. Then, rotate the cord and the flag raises high on the pole.

If two or more simple machines work together as one, they form a compound machine. Most of the machines we use today are compound machines, created by combining several simple machines. Can you think of creative ways to combine simple machines to make work easier? Think about it.

When we use a machine to simplify the work or to use less force to do a work, we have some mechanical advantage. The mechanical advantage of a system is defined as the ratio of the force that performs the useful work to the force applied, assuming there is no friction in the system.

Need more details?

or different way of explaining the above material?

Continue to read about simple machines.

Simple machines are types of machines that do work with one movement. There are 6 simple machines; the inclined plane, the wedge, the screw, the lever, the pulley, and the wheel and axle.

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INCLINED PLANE : An inclined plane is a simple machine with no moving parts. It is simply a straight slanted surface. ( Ex. a ramp.)

An inclined plane is a slanted surface used to raise an object. A ramp is an inclined plane. When an object is moved up an inclined plane, less effort is needed than if you were to lift it straight up, but, you must move the object over a greater distance. To elevate a roller coaster, it is much easier to pull it up a ramp than it is to lift it straight up. http://home.a-city.de/walter.fendt/phe/inclplane.htm

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WEDGE: A wedge is a modification of an inclined plane that moves . It is made of two inclined planes put together. Instead of the resistance being moved up an inclined plane, the inclined plane moves the resistance.

A wedge is an inclined plane which moves. Most wedges (but not all) are combinations of two inclined planes. A knife, axe, razor blade, and teeth are all good examples of wedges. Generally it can be anything that splits, cuts, or divides another object including air and water.

In the above examples identify what is being split or wedged apart by each wedge in the above pictures. a rocket…. a fan… a boat… teeth…

a doorstop… (not pictured)

What example did you come up with?

SCREW : A screw is a simple machine that is like an inclined plane. It is an inclined plane that wraps around a shaft.

LEVER: The lever is a simple machine made with a bar free to move about a fixed point called a fulcrum.

There are three types of levers.

PULLEY: A pulley is a simple machine made with a rope, belt or chain wrapped around a grooved wheel. A pulley works two ways. It can change the direction of a force or it can change the amount of force. A fixed pulley changes the direction of the applied force. ( Ex. Raising the flag ) . A movable pulley is attached to the object you are moving.

A pulley is a chain, belt or rope wrapped around a wheel. The mechanical advantage of a pulley system is approximately equal to the amount of supporting ropes or strands.

Therefore, if you had a mass of 60kg and wanted to lift it using two supporting ropes, you would have mechanical advantage (MA) of 2. The mass will feel like one half of what it really is. When lifted with the help of the pulley system your 60kg would only feel like 30kg. Thus the effort force equals 30kg.

http://home.a-city.de/walter.fendt/phe/pulleysystem.htm

For practice figure the following mechanical advantage (MA) problems.

1. If a pulley setup has three supporting strands, what would be the MA of the setup?(3)
2. If the weight of an object being lifted is 100 kg and the number of supporting ropes the pulley system has is four; what would be the systems MA? (4) How much effort weight would you actually be lifting? (25 kg)
3. The weight of an object is 30 kg, the mechanical advantage is three, how much effort weight would you need to raise the object? (10 kg)

WHEEL AND AXLE : A wheel and axle is a modification of a pulley. A wheel is fixed to a shaft. The wheel and shaft must move together to be a simple machine. Sometimes the wheel has a crank or handle on it. Examples of wheel and axles include roller skates and doorknobs.

A wheel and axle is a lever that rotates in a circle around a center point or fulcrum. The larger wheel (or outside) rotates around the smaller wheel (axle). Bicycle wheels, ferries wheels and gears are all examples of a wheel and axle. Wheels can also have a solid shaft with the center core as the axle such as a screwdriver or drill bit or the log in a log rolling contest.

Why is a wheel a lever? Read on.

In the first example the resistance is in the mass of the wheel itself, the axle and whatever it might be connected to. The effort force is applied to the outer wheel. Steering wheels and door knob are good examples. Remember EFR?

The second example (on the right) the effort comes from the axle, the fulcrum is the core of the axle and resistance is on the road. (vehicle wheels are this way) Remember FER?

Now list five of your own examples of wheel and axles. You may use the term wheel only 3 times – be creative!

Question 2 – Identify the effort, resistance and fulcrum of two of your examples from above.

Question 3 – What type of lever is a steering wheel? A bicycle wheel?

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 make working models of some simple machines and demonstrate how they work. We will also attempt to measure the mechanical advantage of each simple machine.

If you want to study on a specific question related to simple machines, following is a sample question.

How does the slope affect the mechanical advantage in an inclined plane?

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.

In each simple machine a different set of variables affect the mechanical advantage of that machine. For example in an inclined plane, the slope and friction affect the mechanical advantage. In a lever, the distance of forces (resistance and effort) from fulcrum affect the mechanical advantage.

In this project we will not focus on the effect of any specific variable or any specific type of simple machine. So we don’t need to identify variables. However if you choose to study on a specific variable, this is the way that you define variables:

For the question of “How does the slope affect the mechanical advantage in an inclined plane?”, the slope of an inclined plane is an independent variable. The mechanical advantage is a dependent variable.

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.

As a display project we will not need to come up with a hypothesis. However if you want to study on a specific variable such as the slope of an inclined plane, following is a sample hypothesis:

I hypothesize that lower slope in an inclined plane results a higher mechanical advantage (simpler work)

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.”

Following are some experiments that you can choose for your project.

Experiment 1: What happens to the amount of work needed to move a resistance

when the distance of the inclined plane increases (or the slope decreases)?

Materials:

spring scale
weight
ruler or similar piece of wood (1ft)
shoebox
yardstick

1. Place the shoebox on a tabletop.
2. Place one end of the ruler on top of the shoebox and the other end of the ruler on the tabletop.
3. Put the weight on the lower end of the ruler.
4. Attach the spring scale to the weight.
5. Slowly move the weight up the inclined plane to rest on the top of the shoebox.
6. Read the spring scale as you move the weight.
7. Next replace the foot ruler with the yardstick.
8. Repeat steps 2 – 7.

Note: Instead of ruler and yard stick, you can use any long flat piece of wood. Also for changing the slope or angle, you can make any other arrangements that is possible for you.

Repeat the test with different angles. Note that if the surface is horizontal (angle is 0), all the force shown by the spring scale is caused by friction. Instead of a simple block of wood as weight, you can use a toy car to have less friction and better results.

Imagine the weight of a toy car is 80 grams, but when you pull it up on a 30 degree ramp, the spring scale shows only 40 grams. In this way the mechanical advantage of your inclined plane is 2. (Divide 80 by 40)

Experiment 2: What happens when the wedge is pushed between the stack of books?

Materials:

four hard covered books
a wedge
a tabletop

1. Stack the books on the tabletop vertically.
2. Place the tip of the wedge between the second and third books.
3. Push the wedge between the books.

Note: For best results place the books next to the wall so they will not fall by the force. Instead of books you can also use wood blocks. The wedge also can be a wooden wedge.

Experiment 3: Which screw is the easiest to screw into a block of wood?

Materials:

• • one block of wood
  • four screw the same length with various numbers of threads

1. Take the screw with the least number of grooves.
2. Screw it into the block of wood.
3. Take the screw with the second least number of grooves.
4. Screw the second screw into the block of wood.
5. Take the screw with second to the most grooves.
6. Screw it into the block of wood.
7. Take the screw with the most grooves.
8. Screw it into the block of wood.

1. Draw each type of lever for your display, label the fulcrum, effort, and object to be moved (or force).

2. Find other examples of levers and classify them as first, second, or third class.

Experiment 4: What happens when the distance is changed between the fulcrum and the effort force?

Materials:

• • 5 large washers taped together (as weights)
  • 30 cm ruler (as a lever)
  • pencil (as fulcrum)

1. Place washers on top of ruler at the 1 cm mark.
2. Place the pencil under the ruler at the 10 cm.
3. Push down on the 30 cm mark (effort force).
4. Move pencil to 15 cm mark and again push down at 30 cm mark (effort force).
5. Compare your effort force in steps 3 & 4.
6. Move pencil to 20 cm mark and again push down (effort force).
7.What class lever is this?

Note: You can use any other piece of wood as a lever. Also many objects can serve as a fulcrum. Bolts, washers and pennies are among the material that you can use as weight.
You will modify the distance between the weights and the fulcrum. Place one bolt (or any other weight) on one end of the lever, the place 3 weights on the other side, in a position that creates a balance.

Experiment 5: What happens when you increase the number of pulleys ?

Materials:

• • three students
  • two broom handles
  • one ten foot long piece of twine or rope

1. Have one student tie the end of the twine onto one of the broom handles.
2. Have two of the students stand about two and one half feet apart so that the broom handles are held about two feet apart.
3. Wrap the twine around the broom handles twice.
4. Have the third student pull on the twine as the other two students try to hold the broom handles apart.
5. Now wrap the twine around the broom handles two more times and repeat step

Make a Simple Pulley

Procedure:

1.Cut the bottom of the coat hanger and insert the spool into the open ends of the wire.

2.Adjust the wire so that the spool turns easily, and then bend the ends down to keep the wires from spreading.

3.Screw a cuphook into a fixed board.

4.Hang the coat hanger pulley on the cuphook.

5.Loop a string once around the spool.

6.Attach a weight, such as a book, to the end of the string.

7.Pull the string to lift the weight.

8.What would happen if you used two pulleys instead of only one?

Experiment 6:

How does the simple machine called the wheel and axle make work easier?

Materials:

empty spool of thread
string
paper cup
20 pennies
2 pencils
tape

Sample Hypothesis: Wheel and axle can trade force with distance. With little force we can pull down the cup A so that the heavy cup B moves up; however, cup B travels an upward distance that is less than the downward move of cup A.

Procedure:

1. Push pointed end of pencils into each end of the thread spools (make sure they are secure)
2. Suspend the pencils from the edge of a table with two loops of string–make sure they are level. Tape the string to the table.
3. Punch holes at the top of each paper cup. Attach a 60 cm string to each cup. Mark the cups A and B.
4. Tape the string attached to cup A to the pencil and wind all of the string onto the pencil by turning the pencil away from you.
5. Tape the string attached to cup B to the thread spool . Turn the pencils toward you to wind up all of the string onto the spool.
6. Place 10 pennies in cup A.
7. Cup B should be at its top position. Add pennies to cup B one at a time until it
starts to move slowly.
8. Observe the distance both cups moved.

Materials and Equipment:

List of material can be extracted from the experiment section.

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:

You will need to calculate the mechanical advantage of each simple machine that you make. To do that divide the load (or the force that performs the useful work) by the effort (or the force applied) assuming there is no friction in the system.

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. 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:

http://lyra.colorado.edu/sbo/mary/play/lever.html

http://home.a-city.de/walter.fendt/phe/lever.htm

http://home.a-city.de/walter.fendt/phe/phe.htm