Table of Contents
Career Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Basic Lesson Plans
Activity 1 – Measuring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Activity 2 – Accuracy and Precision. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Activity 3 – Measurement Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Activity 4 – Exploring Density. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Challenge 1 – Rocky Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Activity 5 – Simple Machines: Levers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Activity 6 – Simple Machines: Pulleys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Pulley Extension Activities (optional). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Challenge 2 – Rube Goldberg Machine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Standards Addressed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Puzzles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Links of Interest. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
3
Activity 6
Simple Machines: Pulleys
Teacher Procedure
Objective
Two common ways to use a pulley to lift a load
is with a fixed pulley or movable pulley.
Students experience the mechanical advantage
provided by pulleys or a pulley system.
Fixed pulley – the frame is attached to a ceiling
or beam and the load is attached to the cord.
This allows the load to be moved upwards by
pulling downwards from the ground (like the
pulley on a flagpole).
Simple machines offer mechanical advantage,
which makes a task easier or require less force.
However, it may require more time or room
to work. For example, applying a smaller force
over a longer distance to achieve the same
effect as applying a large force over a small
distance. The ratio of the output force exerted by
a machine to the input force applied to it is the
mechanical advantage of the machine.
“Engineers are experts at exploiting the
advantages of simple machines in all sorts of
real-world applications that benefit society. They
incorporate the mechanical advantage of pulleys
into their design of many modern-day structures,
machines, products and tools, such as cranes,
elevators, flagpoles, zip lines, motors, bicycle
rings/chains, clothes lines, water well bucket/
rope, rock climbing devices, window blinds,
and sail/fishing boats. Using multiple pulleys
in conjunction with motors and electronics,
engineers create complex modern devices that
perform much work for very little power.”
– Integrated Teaching and Learning Program,
College of Engineering, University of Colorado
at Boulder
Rope
10 kg
Object
Force
10 kg
Movable pulley – the cord is fixed to a ceiling
or beam and the load is attached to the frame.
The load is raised by pulling up from a higher
level.
Attached
MA = 2
Force
5 kg
Load-supporting rope
Pulleys are an excellent example of the
mechanical advantage offered by simple
machines. A simple pulley consists of a wheel
with a groove around the edge, set in a frame.
Pulleys are used to change the direction of a
force. The force is applied to an object by the
tension in a cord that lies in the pulley’s groove.
The frame is used to attach the pulley to a fixed
object (like a ceiling) or to a load.
Pulley
Load-supporting rope
Background
Pulley
10 kg
47
Object
Activity 6
Simple Machines: Pulleys
Teacher Procedure
Engineers often combine fixed and movable
pulleys into systems to gain a mechanical
advantage or greatly reduce the amount of force
required to move an object. You will notice
in the pictures below that the second system
requires only half the force to lift the same
amount of material as the first. The mechanical
advantage, MA, determined by counting the
number of load-supporting ropes, is twice as
high.
Procedure
1
Following the Student Procedure, have
students build fixed, movable, and
combined pulley systems to learn about
mechanical advantage.
Load-supporting rope
Attached
Movable
Pulley
Object
Redirecting-only rope
Fixed
Pulley
Load-supporting rope
MA = 2
Force
5 kg
10 kg
Attached
Fixed
Pulleys
MA = 4
Force
2.5 kg
Loadsupporting
ropes
Movable
Pulleys
10 kg
48
Activity 6
Simple Machines: Pulleys
Student Procedure
Vocabulary
•
•
•
•
•
•
effort
fixed pulley
force
load
mechanical advantage
movable pulley
Materials
•
•
•
•
•
•
Forces & Simple Machines Kit
Hooked 100-, 200-, 300-gram weights
Spring scale
Pulley
Cord
“Pulley Data Sheet”
Procedure
1
Screw the support rod into the tripod base
and attach one of the hooked collars to
the upright support rod about three centimeters
above the base with the open end of the hook
pointing downward.
2
Attach the second hooked collar to the
support rod near the top with the hook
pointing upward.
3
Tie a loop on each end of the length of
pulley cord.
The Fixed Pulley
1
Hang the pulley from the upper hooked
collar, thread the cord through the top of
the frame, and lay it into the pulley groove.
2
Attach a weight hanger to the left end
of the cord and the upper hook of the
spring scale to the right end. Add weights to
the weight hanger until the weight of the spring
scale is balanced and the weight hanger does
not move up or down when released.
3
Now attach the spring scale’s lower
hook to the lower hook collar and add a
100-gram weight to the weight hanger.
4
Read the value shown on the spring scale
in grams and record it on the “Pulley Data
Sheet.”
5
Exchange the 100-gram weight for a
200-gram weight and record the new
spring scale value.
6
Now unhook the lower spring scale hook
from the hook collar and, holding the
lower spring scale hook, move the spring scale
outward to several different angles. Note what
happens to the reading of the spring scale when
you do this.
49
Activity 6
Simple Machines: Pulleys
Student Procedure
The Movable Pulley
1
Remove the spring scale and weight hanger
and unhook the pulley frame from the
upper hook collar.
2
Attach one end of the cord to the upper
hook collar, thread the cord through the
lower end of the pulley frame, lay the cord into
the pulley groove, and attach the free end to
the spring scale’s lower hook. (You may hang
the spring scale’s upper hook onto the upper
hook collar while setting up.)
3
Add 100 grams of weight to the weight
hanger and hook it onto the lower end of
the pulley frame.
4
Hold the spring scale by the upper hook
so that the pulley cords are close to vertical
and record the spring scale value in grams.
5
Repeat this measurement with 200 grams
and 300 grams on the weight hanger.
50
Activity 6
Simple Machines: Pulleys
Student Procedure
Pulley Data Sheet
Fixed Pulley
Load (g)
Spring Scale Reading (g)
100
200
300
1. What did you notice when you moved the spring scale to different angles?
2. How does the spring scale reading (the effort) compare to the load?
3. Does the fixed pulley offer a mechanical advantage?
4. Does the angle of effort make a difference?
Movable Pulley
Load (g)
Spring Scale Reading (g)
100
200
300
1. How does the spring scale reading (the effort) compare to the load?
2. Does the movable pulley offer a mechanical advantage?
3. If you wanted to lift a large load, would it be easier with a fixed pulley or a movable one?
51
Pulley Extension Activities
Student Procedure
Vocabulary
• tandem pulley
Materials
• All materials from the Simple Machines:
Pulleys activity
• Extra pulleys
• Tandem pulleys
• “Pulleys Extension Data Sheet”
Procedure
Single-Pulley System
1
Hang one of the single pulleys onto the
support rod. (You may have to open the
eye slightly to make it fit.)
2
Attach one of the pulley cord loops of
the shorter cord to the upper hook of the
spring scale and temporarily hang the spring
scale from the support rod’s thumbscrew.
3
Thread the other end of the cord through
the top of the pulley frame and then
through one end of the second pulley frame.
Then slide the loop at the free end of the cord
over the support rod.
4
Hang the weight hanger from the lower
hook of the movable pulley and hold the
spring scale in your hand near the bottom of
the vertical support rod. Now place the cord
into the grooves of the pulleys.
5
Add weights to the hanger until the
weight of the spring scale is a little more
than balanced (the spring scale tends to move
upward).
6
Add a 100-gram weight to the hanger and
record the value of the spring scale reading
(the effort) in grams on the data sheet.
7
8
Add weights and record the spring scale
readings for loads of 200 and 300 grams.
Note that there are two strings supporting
the load and the movable pulley. Record
this.
Tandem (Four and Six) Pulleys
1
Hang one of the tandem pulleys onto the
support rod with the largest pulley at the
top.
2
Attach the loop of the longer cord to the
lower eye of the tandem pulley.
55
Pulley Extension Activities
Student Procedure
3
Hold the second tandem pulley below the
first with the smallest pulleys facing each
other.
4
Thread the cord carefully through two sets
of pulleys. Make sure the cord is securely
in all the grooves.
5
6
Hang the weight hanger and add 100
grams.
Keeping hold of the free end of the cord,
attach the spring scale’s upper hook to the
hook collar and tie the free end of the cord to
the spring scale’s lower hook.
7
8
Add weights to balance the spring scale
and zero it as before.
One at a time, switch out the 100-gram
weight for the 200-gram, 300-gram, and
400-gram weights. Record the values on your
data sheet.
9
Add two more pulleys and record the
differences.
56