Title: Simple Machines
Author: David Cox
taken from Project ASPIRE at the University of Utah
Subject: Physical Science
Grade Level : 7-8th Grade
Description of lesson:
Students will investigate the use of the wedge to accomplish work in a direction different from the force
initially applied, with particular attention to the selection of the most appropriately shaped wedge given to
them on an online interactive web activity.
Students will also collect data as they exert force on a lever through varying distances to accomplish a
desired amount of work. They will calculate the mechanical advantage of the lever and determine the
appropriate force to lift a block.
Length of lesson : 1- 45 min period
Lesson Objectives:
After investigating the work accomplished by applying force, students will be able to:
1.
2.
3.
4.
5.
6.
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.
Materials:

Computer(s) with Internet connection (Calculator)

Web site: http://sunshine.chpc.utah.edu/javalabs/java12/machine/index.htm

Student Lab Packet - This is a printable version of the lab materials (instructions, tables,
and questions).
For the prep: 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.

Prep for lesson :
1. 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.
2. 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.
3. 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.
4. 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.
Pre-Assessment:
The questions asked in the prep for lesson, 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.
Procedure:
Each student should have a lab packet to record their data and responses.
Invite students to proceed to the Student's Introduction where the 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.
Scientific Explanation:
We are surrounded by the use of machines to construct and maintain buildings and roads. We see
massive objects raised and lowered into position. Large machines can literally move mountains over a
period of time. As we maintain our homes, make repairs, move furniture, clean and pick up our "stuff" we
utilize simple machines. Some of which are actually part of our physical make up.
These labs will help students recognize simple machines as they are used by them and around them.
They will be able to calculate the amount of work done and utilize simple machines to accomplish work
more easily.
Most modern machines are combinations of the six simple machines. These devices rely on a few simple
principles. Work is defined as the movement of a force through a distance. The simple machine can not
reduce the amount of work needed to complete a task, however, it can reduce the effort needed from the
user.


Work = F x D
F(resistance)D(resistance) = F(effort)D(effort)
The Force applied (FE) times the Distance the effort must move (DE) equals the work done by the
effort force.
The Force of the resistance (FR) (frequently the weight of the object to be moved) times the
distance the resistance moves (DR) is the work done.
If (FR) > (FE), then (DR) < (DE)
By increasing the distance the effort moves, the amount of effort can be reduced.
Increasing the effort force applied reduces the distance it must move to accomplish the same amount of
work.
A third advantage to be gained by using a simple machine is changing the direction of the force.
These activities use SI units (the metric system).


The SI unit for weight and other forces is the Newton (N).
(4.45N = 1 pound)
The SI unit for the distance or length is the meter (m).
(1 meter = 3.28 feet, 2.54 cm = 1 inch)
Assessment:
Questions completed at the end of the activities will check the understanding of the basic
concepts. ( see Student Lab Packet)
Extension:
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:
1.
2.
3.
4.
5.
6.
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.
Kansas Standard:
STANDARD 2: PHYSICAL SCIENCE Grades 5-7
PHYSICAL SCIENCE – The student will apply process skills to develop an understanding of physical
science including: properties, changes of properties of matter, motion and forces, and transfer of energy.
Benchmark 3: The student will investigate motion and forces.
Objective 4. investigates and explains how simple machines multiply force at the expense of distance.
Missouri GLE’s:
Strand 2: Properties and Principles of Force and Motion
2.Forces affect motion
Concept F.
Work transfers energy into and out of a mechanical system
Scope and Sequence – Work and Simple Machines Grade 5
a. Explain how work can be done on an object (force applied and distance moved) (No formula
calculations at this level)
b. Identify the simple machines in common tools and household items
c. Compare the measures of effort force (measured using a spring scale to the nearest Newton) needed
to lift a load with and without the use of simple machines
d. Observe and explain that simple machines change the amount of effort force and/or direction of
force