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Objectives |
Materials |
Invitation To Learn |
Lab Procedure |
Closure
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Lesson Objectives:
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After investigating the work accomplished by applying force, students
will be able to:
- Describe two of the simple machines, the wedge and the lever.
- Describe how each of these machines can make work easier.
- Represent data in a table and calculate the mechanical advantage.
- Construct a graph showing the relationship of force to effort.
- Make predictions using the data in the graph.
- Recognize examples of levers and wedges in their surroundings.
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Background:
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Preliminary Knowledge:
- Basic math skills.
- Graphing skills.
- Units of measure for force (Newton N), and distance (meter m).
- Basic vocabulary: force, work, fulcrum, lever, effort,
resistance, wedge.
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- Computer(s) with Internet connection (See our Technical Support page for assistance.)
- Calculator
- Student Lab Packet - This
is a printable version of the lab materials (instructions, tables,
and questions).
- For the Invitation To Learn: wedge-shaped door stop, paint can or
other metal-topped container with an inset lid, coin, screwdriver,
can opener (church key). For each pair or team of students: 10
pennies, a ruler and a pencil.
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- Challenge a student to hold a door shut against the efforts of
another student to open it. Be sure to assign an appropriately
assertive student to push the door open. Allow the holder to place
one student desk in front of the door if they wish. After at least
one failed attempt, provide the student holding the door with a
wedge-shaped door stop to help. Discuss all results and ask for
volunteered theories.
- Present a closed paint can and/or other metal-topped container with
an inset lid (powdered milk mixes, baking powder can), and ask
someone to open one. Use fingers, a coin, scissors (careful, school
scissors often break), screwdriver, can opener (church key). Take
suggestions from the group for ways to open the can. Discuss the
relative success of all methods. Ask for explanations of what did
and didn't happen and why.
- There are several terms with which students must be comfortable.
Simple machines are first introduced in the primary grades. A
reintroduction to the vocabulary could be accomplished by grouping
students in fours, perhaps two sets of computer partners. Assign
each student to demonstrate to their group the meanings of
two of the vocabulary words. This gives each person a small but
specific assignment and removes vocabulary from the realm of a
paper/pencil activity.
- Provide each pair or team of students with a ruler (lever arm),
pencil (fulcrum), and about ten pennies or comparable weights.
Challenge them to balance five pennies with five pennies, six with
four, eight with 2, etc. Discuss relationships and adjustments made.
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Pre-Assessment:
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The questions asked in the Invitation To Learn should give a good
assessment of where the students stand with their background knowledge.
One aspect not covered there is work. Perhaps generating a list
of "What Is Work?" will give insight into their understanding
of this concept. Each lab worksheet calls for prediction before
completing the activity.
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Directions for Teaching the Lab:
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Each student should have a lab packet to record their data and
responses.
Invite students to proceed to the Student's Introduction where they
will be introduced to simple machines, and the idea of Mechanical
Advantage. Encourage discussion with their partners.
Students are frequently asked to discuss their answers and predictions
with their partner. Monitor this activity to help students share their
ideas and value their partners as well. They should then
return to the lab menu and proceed to the student lab.
As they enter the lab, they are introduced to the problem of splitting
large blocks of rock for use in construction. The simple
machine used is a wedge. Work and mechanical advantage are not
addressed here. They will experiment with wedges of various
proportions to determine the most effective shapes and sizes.
Encourage them to test a variety of shapes from very elongated to
almost flat.
They will enter data on a chart and graph the wedge proportions and
indicate where the effective shapes fall on the graph.
As they complete the questions about the wedge, they will scroll
down to the activities related to levers.
Use of complete sentences in answering questions is emphasized to insure
students are able to express underlying ideas completely and to reinforce their
understanding of the concepts. It is important that you discourage the use
of single word or phrase answers.
The problem presented is to lift the cut stone onto a cart. Students
are asked to state their knowledge of levers and work before
proceeding.
They will test several levers by repositioning the fulcrum. Effort
force and the distance through which it moves are recorded on a chart.
Using the data from the lever trials, students calculate work done and
then the mechanical advantage.
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Summary:
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This lesson will introduce students to the wedge and lever. They will
be able to calculate work input, work output, and mechanical advantage.
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Post-Assessment:
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Questions completed at the end of the activities will check the
understanding of the basic concepts.
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Extension:
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Challenge students to identify the
fulcrum, placement, and direction of both the effort force and the
resistance force on a variety of levers. Such as:
- A broom (this will vary depending upon how the broom is used)
- Oar on a boat
- Bottle cap opener
- A coin used to open the battery compartment of a toy
- A pry bar or a claw hammer
- A pole used to lift or move a rock
Assign students to keep record of the use of any wedge or lever they
see for a day. Perhaps these could be listed on a bulletin board or
on a simple machines "graffiti wall" within the classroom.
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