| Mystery Machines |
| Grades 3-4 |
Lesson #40 |
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There is no video with this lesson |
| Educational Objective |
Students will learn about simple machines and demonstrate their
acquired understanding by designing a simple machine.
Associated Standard and CORE Objectives:
- 3030-0401 - Demonstrate how machines make work easier.
- 3030-0402 - Classify forces as pushes and pulls.
- Demonstrate how levers working with fulcrums can lift various objects.
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There are six different simple machines; lever, wedge, inclined plane, screw, pulley, and wheel
and axle. |
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Materials List:
- Lever with fulcrum
- Gear trains (sample machine)
- Pulley stand
- Simple machine board
- Car jack (sample simple machine)
- Tow truck (sample multiple machines)
- 2 - Incline planes with cars (sample simple machine)
- 2 - Levers (sample simple machine)
- 1 - Large lever with weight and gauge (sample simple machine)
- Machine Muncher Game Kit:
- 8 - Cups
- 16 - Chips: 8 with a #5 written on it, 8 with a #10 on it
- 8 - Mini-teeter-totters
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| Preparation |
Teacher provides drawing paper, rulers pencils and colored markers for Group #2 activity |
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Cover lever with fulcrum prior to students entering classroom, have two different areas of
classroom for the activities and game already set up and ready to go. |
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View lesson on separate page |
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Lesson |
| Review Definitions |
kinetic energy
potential energy |
| Introduction |
Have a student volunteer come up. Ask if it is possible
to lift a book into the air without touching it.
Brainstorm: Let students come up with
a variety of answers, discuss, compare and contrast.
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| Uncover lever with fulcrum |
Uncover lever with fulcrum and students will probably get the answer to the
question. Place the book on one side of the teeter-totter at the far end.
Have the student push on the opposite end and it will put the book into the
air.
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| Talk about the force |
Talk about the force that was exerted to get the book airborne.
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| Re-adjust |
Re-adjust with the end to be lifted further from the fulcrum. Is it easier
or harder to raise the book into the air? (Harder) Re-adjust the fulcrum
again with the end to be lifted closer to the fulcrum. Ask: Is that easier
or harder than last try? (Easier)
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| Discuss fulcrum |
Discuss that the object in the middle is called the fulcrum. Ask: Why
do you think that placing the fulcrum in different locations made it easier
or harder to lift? Explain that the closer the object is to the fulcrum, the
easier it is to lift it. This is referred to as "mechanical advantage". |
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| Ask |
Ask: Does anyone know the name of something that uses a fulcrum as in the
teeter-totter? (Lever) Simple machines that use a lever can make work easier
for us. Show the lever with a fulcrum. There are other objects that help
make work easier too, such as a pulley.
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A simple machine can do two things: multiply a force, or change
the direction
of a force. |
| Single pulley |
This demonstration uses pulleys to lift an object. Each object
has the same mass, but using the pulleys we can change how "heavy" the object feels.
Find the system with only one pulley.
Lift the weight with your hand and get a sense for its heft.
Now lift the weight by pulling down on the end of the rope that rides over the pulley. The heft of
the weight in these two cases should feel about the same.
The advantage of using the machine in
this case is that rather than having to bend over and lift the weight you can simply pull down on
the rope to lift the weight. Imagine trying to lift a 100 kg hay bale up to the second story of a
barn using your legs and back to carry it up the stairs. Certainly it would be much easier to just
haul it up on a rope using a pulley.
The Mechanical Advantage of a pulley system is approximately
equal to the number lines that are attached directly to the load or attached to the pulley that is
attached to the load. These lines are known as "support ropes". The number of support ropes is
about the same as the mechanical advantage of the system. |
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| Two pulley system |
Now consider the two pulley system. This set up contains what is known
as two support ropes. When you lift the mass by pulling on the rope in
this case, the weight feels much lighter than
on the single pulley system.
By using two support ropes this system has a
mechanical advantage of two.
This means that whatever force you apply
to the rope gets multiplied by 2 in the machine.
Note that the mass of this system "feels" about half as heavy as the single
pulley system. In this case the weight stays constant, but your effort force
is cut in half.
If we had a fixed effort force,
we could use the pulley system to double the amount of weight we could lift
without changing the
"feel" of how much force we apply to lift the weight. For example, if you weigh
50 kg you could lift a mass of 100 kg by using a pulley with two support ropes
(50 x 2 = 100).
Using this machine to double your lifting ability does have a drawback. When
using machines nothing is free, there is always a price to pay. The price
in this case (a 2x mechanical advantage) is that you must move your end of
the rope twice as far as the object being moved. For example, lets say our
50 kg person wants to lift the 100 kg object to a height of 5 meters. The machine
with
a mechanical advantage of 2x will multiply the 50 kg effort force by 2 and
allow the person to lift the 100 kg mass, but the person will have to pull
their end of the rope 20 meters in order to lift the object 10 meters. |
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| Predict the three pulley system |
Predict how the three pulley system will work. Ask students for their thoughts. Can the class come to a consensus? Have a student demonstrate the three pulley system and describe the experience as compared to the one and two pulley system.
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| Using a lever |
When using a lever to demonstrate simple machines, the mechanical advantage
is approximately equal to the length of the effort arm divided by the length
of the resistance arm. Consider a lever where the fulcrum is exactly between
the effort force and the resistance force.In this case the effort and resistance
arms are of equal length, thus the mechanical advantage is 1:1. |
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| If we adjust the fulcrum |
If we adjust the fulcrum so that the effort arm is 6 feet long and the
resistance arm is 3 feet long, the mechanical advantage is now 6/3, or
2x. This means
that whatever force we place on the effort arm will be multiplied by two
on the resistance arm. For example, if a student weighs 30 Kg, she would
be able to move 60 Kg on the other end of the lever. Once again, there
is
a price to pay for
being able to lift twice your weight; that price is distance. If our student
wants to lift the 60 Kg object 50 cm off the ground, she has to move her
end of
the lever 100 cm (two-times as far). If our student wanted to lift a 50 Kg
object 30 cm high, how could she use a lever to do it? What will the lengths
of the effort and resistance arms have to be? |
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| Observation |
Take a few minutes and have students observe your classroom looking for simple machines that are part of your room. Make a list of these simple machines found, post them on the board along with a simple drawing of the machine.
Discuss how your classroom might function, or not function, if these simple machines did not exist. Ask students how other simple machines could be used in your classroom to make the room more functional. Again, list ideas on board with simple drawings.
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| Now we will get some hands-on experience |
Now we will get some hands-on experience with levers and other simple machines.
Explain game rules and lever activity before dividing class into two groups.
Group #1 will play Machine Muncher, Group #2 will divide into sub-groups of 3 and view the sample simple machines in the unit.
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| Use one, two or all three of the activities listed below! |
Activity #1
Machine Muncher Game |
- This game is to be
played in pairs.
- It works best to play it on the carpet.
- Make a lever using
tongue depressor and fulcrum.
- Place lever in front of container.
- Students
take turns trying to catapult chips into container.
- Each person gets one
chance at catapulting the #5 and the #10 chip on a turn.
- Each one keeps track
of his/her points.
- One chip has a #5 for 5 points and the other one has a #10
for 10 points.
- If a student misses the container with a chip, no points are
given.
- Game continues until a student reaches 50 points or highest number of
points when time is over.
- Students can experiment by changing fulcrum position
with lever to see which position works easiest.
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Activity #2
Machine Design |
Your task as a group is to design on paper a machine, using as many simple machines as needed, to complete ONE of the following tasks:
- Shoot a basketball into the hoop without touching the ball with any part of your body.
- Dig a tunnel in a sand hill that measures 4 feet across large enough to put a "matchbox" car through without directly touching the sand.
- Clear off dirty dishes from the kitchen table and put them in the sink without touching any part of the dishes with your body. The table is permanently located 10 feet from the sink.
You will not actually build the machine but will draw it on paper clearly labeling all parts and telling what the machine does and how the machine works.
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| Activity #3 Roll-a-kid! |
Using the two tubs and large dowels for this activity. Divide your group into two teams. Each team will choose one person (the smaller the better) to roll in the tub.
- Establish a course in your room. This could be a straight line or you may choose to put turns into the course.
- The object of this activity is to roll the student sitting in the tub through the course you established.
- One other student per team will be assigned the force behind the tub. (They will push)
- Each other student in the group will be assigned their own dowel. Their job is to place, in turn, their dowel on the roadway in front of the tub then retrieve it out the back as the tub is rolled along.
- Dowel students repeat this action until their tub crosses the finish line.
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| Switch Activities |
The groups switch activities half-way through the remaining time.
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End of Lesson |
| Conclusion |
Have students make sure kits are complete, clean up areas and come back as large group. Ask what
they discovered or if they learned anything new to share with the group.
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| Extensions |
Make Machine Muncher Games for students to take home.
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| Background Information |
There are five different simple machines; lever, inclined plane, screw, pulley, and wheel
and axle
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| This lesson relates to the following |
Career Fields Science, Technical
Occupations:
- Mechanical Engineer: Plan and design tools, engines, machines, and other mechanical equipment. They design
and develop power-producing machines such as internal combustion engines, steam and gas turbines, and jet and rocket
engines. They also design and develop power-using machines such as refrigeration and air-conditioning equipment,
robots, machine tools, materials handling systems, and industrial production equipment.
Education: Bachelor's Degree
- Construction Equipment Operator: Use machinery to move construction materials, earth, petroleum products,
coal, grain, manufactured goods, and other heavy materials. They operate by moving levers or foot pedals, operating
switches, or turning dials. They may also set up and inspect equipment, make adjustments, and perform minor repairs.
Education: On-the-job training
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| Review Questions |
- Can you think of real life examples where machines make work easier?
- How about examples with gears and pulleys?
- How did the "come back can" illustrate potential and kinetic energy?
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