Pulleys
UNIT: PULLEYS
OVERVIEW
INTRODUCTION
In this unit students will build on their knowledge of Simple Machines by building a pulley frame that can lift weights and also a block and tackle system that raises
the arm of a Crane.
STANDARD NCF ALIGNMENT
SCIENCE
• Idea of force-push or pull; change in speed, direction of moving
objects
MATHEMATICS
• Conversion of units of length between smaller and larger units
ENGLISH LANGUAGE ARTS
• To be able to articulate individual/personal responses effectively
• To use his/ her proficiency in English to explore and study other areas
of knowledge through print and non-print media
• To be able to narrate simple experiences, describe objects and
people, report events to peers
1
Pulleys
OVERVIEW
CREYA OUTCOMES
ANALYTICAL THINKING
COLLABORATION • Analyzing information: data, ideas, or concepts
• Contribution to team
• Applying formulae, procedures, principles, or themes
• Working with Others
• Presenting multiple solutions, positions or perspectives
• Time Management
CREATIVE THINKING
• Ideation/Brainstorming
• Originality
INFORMATION FLUENCY - JOURNALING
•
Format
•
Mechanics
•
Proper spelling and grammar
• Flexibility in approaches
PROBLEM SOLVING
• Define the problem
• Identify Strategies
• Propose solutions/Hypotheses
• Implement the solution
2
INFORMATION FLUENCY - INFORMATION LITERACY
•
Access the needed information
Pulleys
PREPARATION
PROJECT 1: PULLEY FRAME
PROJECT 2: PULLEY CRANE
Overview:
In, Pulley Frame, students will build a frame and lift a
load with pulley systems.
3
Overview:
In the, Pulley Crane, students will use a block and
tackle system to raise and lower a crane arm.
Materials:
Materials:
4 - Hinged Block Claw
15 - Building Block 30
2 - Building Block 15
2 - Building Block 15 with 2 Pins
4 - Building Block 15x30x5 with Groove and Pin
4 - Bearing Sleeve
1 - Bottom Plate 30x90
1 - String
4 - Tire 45
4 - Hub Nut
4 - Hinged Block Claw
4 - Spacer Ring
9 - Building Block 15 with Bore
15 - Building Block 30
2 - Building Block 15 with 2 Pins
4 - Flat Hub Collet
2 - Clip Axle 30
Preparation Tips:
Preparation Tips:
Be gentle with raising and lowering the load on the pulley frame. Rough usage
with the pulley system can break the frame.
Pay attention to which pulley the string rests on.
1 - Clip Axle 45
1 - Axle Coupling
2 - Clip Axle 75
1 - Crank Shaft
5 - Bearing Sleeve
2 - Building Block 7.5
3 - Clip 5
1 - Mounting Plate 15x45
1 - String
Pulleys
BACKGROUND
About Pulleys
How do you raise a flag on a tall flagpole, without
standing on top of it? Most flagpoles use a pulley. A
pulley is a simple machine made with a rope, belt,
or chain wrapped around a grooved wheel or similar
device. Pulleys are generally used to raise, lower, or
move a load. A pulley changes the direction of the
pull, or effort. When you pull down on a flagpole’s rope, the flag will rise. A single pulley makes a job
seem easier by letting you pull with the force of
gravity instead of lifting against it. For example, you
are asked to raise a 50 kilogram weight. If you tie a
rope to the weight and try to raise it, you have to pull
up something weighing 50 kilograms. If you run the
rope around a pulley, you are pulling down; it seems
slightly easier because you can use your own weight
as a counterweight. A fixed pulley does not rise or
fall with the load being moved, and does not create a
mechanical advantage.
One of the properties of a simple machine such as the
pulley, is that is it can be used to magnify the force
applied to a task. The mechanical advantage of a
4
machine is the number of times a machine multiplies
the effort, and is the ratio of the output force to the
input force. A moveable pulley rises and falls with the
load that is being moved and creates a mechanical
advantage. A combination of fixed and
moveable pulleys in a block and tackle
also creates mechanical advantage and
reduces the amount of effort needed to
pull up a load. Block and tackle system
allows heavy object to be lifted with less
force. In a block and tackle, the rope must
be pulled a greater distance as it winds
through several sets of pulleys. The trade-off for less effort is more rope pulled.
If you are pulling down on a rope
on a block and tackle system, the
mechanical advantage is equal to
the number of ropes supporting the
load. Count each end of the rope as
a separate rope.
1
2
For example, two rope ends support a moveable
pulley which is connected to a 100 kilogram weight.
The mechanical advantage is 2 and in this situation,
an effort force of 50 kilograms will lift a resistance
force of 100 kg.
Pulleys
BACKGROUND
Terms
BLOCK AND TACKLE
A block and tackle is a tool often used to lift heavy or hard to reach objects. It consists of two basic parts. The block is a pulley or set
of pulleys fitted in a frame. The block is usually attached to a stationary object. The tackle is the rope or cable that runs through the
block and anything else needed to make the machine work. Some tackles, like the one in the picture, use moving pulleys as well as
the rope. The rope will move through the block and, together, the block and tackle can be used to help one person lift a lot more
than they could without it.
FIXED PULLEY
A fixed pulley is a pulley that is fixed into one place.
MOVEABLE PULLEY
A moveable pulley is a pulley that moves along a rope or chain as it is pulled. It is the opposite of a fixed pulley.
PULLEY
A pulley is a wheel with a groove around the edge. Pulleys can be used as a simple machine to change the direction of a pulling
force. By throwing a rope or chain over a pulley, you can lift something up by pulling down.
MECHANICAL ADVANTAGE
Mechanical advantage is the upper hand you gain when you use a mechanical device or machine to help you multiply the amount
of force you can transmit.
Mechanical advantage is expressed mathematically as a ratio or fraction. The top number of the fraction is the force the machine
puts out to perform the work you’re trying to do. This top number is therefore called the output. The bottom number of the fraction
is the force you have to put into the machine to make it do the work, and we call this number the input.
“WOW” Exercises
The following is a class demonstration that allows students to experiment with pulleys.
1. You will need a broom handle or other rigid dowel, duct tape, a length of rope, and a liquid detergent
jug filled with water.
2. Ask students to lift the jug straight up using the rope and broom handle. Have students share their
results.
3. Tape the ends of the broom handle down between two desk tops or other appropriate surfaces. Tie
one end of the rope to the broom hand and loop the rope through the jug handle. Loop the rope
around the top of the dowel, back through the jug handle and loop again around the top of the dowel
again. The jug handle will act as a movable pulley.
4. Have students lift the jug by the free end of the rope. Have students compare the effort between lifting the jug, and using the
pulley system to lift the jug.
5. Compare the amount of rope used lifting the jug with one loop around the dowel, and the amount of rope used with the two loops. Does one system use
more rope than the other?
5
Pulleys
PROJECT 1: PULLEY FRAME
Materials
4 - Hinged
2 - Building
Block 15
15 - Building
Block 30
2
- Building Block 15
1 - String
4 - Building Block 15x30x5
with Groove and Pin
Build
1
2
6
In this project, you
will build a frame and
experiment with lifting
a weight with a single pulley system. You will
compare it to lifting the
weight with a multiple
pulley or block and tackle
system.
Start by building the frame supports. Take four
Building Block 15x30x5s
with Groove and Pin and
connect two of them together to form two sets
of two.
3
4
Place a Bottom Plate
30x90 over the pairs of
Building Block 15x30x5
with Groove and Pin.
Position two Building
Block 15s with 2 Pins
on the frame support
and mount five Building
Block 30s on each of the
Building Block 15s with 2
Pins.
1 - Bottom
Plate 30x90
4 - Bearing
Sleeve
Pulleys
PROJECT 1: PULLEY FRAME
5
6
7
7
Place Building Block 15 on
each of the two columns.
Fix two Building Block 30s
between the two Building
Block 15s.
Attach a Hinged Block
Claw with Bearing Sleeve
beneath each of the two
Building Block 30s. These
Bearing Sleeves and Hinged Block Claws will
serve as fixed immovable
pulleys in a block and tackle. Set the frame aside.
Start the moveable pulley
piece of the block and
tackle. Place a Building
Block 30 on top of two
vertically placed Building
Block 30s.
8
9
Place two Hinged Block
Claws on top of the Building Block 30.
Insert a Bearing Sleeve
into each of the Hinged
Block Claws.
Pulleys
PROJECT 1: PULLEY FRAME
10
Place the moveable pulley
component between
the upright posts of the
support frame.
Finished.
11
8
Run a string from one
of the Bearing Sleeves
on the moveable
pulley component up
to one of the Bearing
Sleeve components
on the frame. Run the
string back down to the
second Bearing Sleeve
on the moveable pulley
component and up and
over the second Bearing
Sleeve component on the
frame.
2
1
4
3
Pulleys
JOURNAL
Pulley Frame
1. Pull the string and make sure it glides smoothly.
2. Redo the string so that it is connected to the weight and
then goes over just one of the frame’s Bearing Sleeves. Try
lifting and dropping the weight several times. Which seems
easier? One pulley or the block and tackle?
Single Pulley: o Block and Tackle: o
3. Repeat the exercise for each pulley system several times. Is there a difference in
the amount of string or the distance you must pull to lift the weights up to the
same height? Which system used a greater length of string?
Single Pulley: o Block and Tackle: o
4. Look up the definition of pulley using a dictionary or any other resource. Define this term in your own words:
__________________________________________________________________
Name: _ _______________________________ Date: _____________________
5. With the string passing over just one pulley, calculate the length of string that
you have to pull to lift the weight 10 cms. Express your answer in metres.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
6. Now repeat this exercise with the original finished model. What is the length of
the string that you have to pull to lift your weight 10 cms? Express your answer
in metres.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
9
7. How is the mechanical advantage calculated in a pulley? Write down in your
own words.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
Pulleys
JOURNAL
Name: _ _______________________________ Date: _____________________
8. Observe the following 4 figures. Now calculate the mechanical advantage of
each pulley system and write it down in the journal below.
a
_________________________________________________________________ ____
c
_________________________________________________________________ ____
10
b
_________________________________________________________________ ____
d
_________________________________________________________________ ____
Pulleys
PROJECT 2: CRANE
Materials
4 -Tire 45
9 - Building Block
15 with Bore
4 - Hub Nut
4 - Spacer Ring
4 - Hinged
Block Claw
15 - Building Block
30
2 - Building Block 15 1 - Mounting
with 2 Pins
Plate 15x45
4 - Flat Hub Collet
1 - Clip
Axle 45
2 - Clip Axle 30
2 - Clip
Axle 75
1 - Crank Shaft
2 - Building
Block 7.5
1 - String
1 -Axle
Coupling
3 - Clip 5
5 - Bearing
Sleeve
Build
1
2
11
In this project, you will
build a model that uses
the form of a block and
tackle to raise and lower
the boom arm of a crane.
You will build a model
that integrates pulleys.
Start with inserting
bearing sleeves into two
Hinged Block Claws.
3
4
Add the Claw-Sleeve
combinations to two
connected Building Block
15s with 2 Pins as shown.
Construct two beams
each with three Building
Block 30s, and join them
together with the above
assembly.
Pulleys
PROJECT 2: CRANE
5
6
12
Add a Building Block 15
with Bore onto each end
of the two beams. Align
the bores horizontally.
You may need to rotate
the model to make yours
match the diagram.
Slide a Clip Axle 75
through the rear
Building Block 15 with
Bore. Place a Building
Block 15 with Bore
between the front-most
Building Block 15s with
Bore and lock the axle
into place with a Clip 5.
7
8
Add a spacer ring and
then a Flat Hub Collets to
all four ends of the axles.
Place a Tire 45 and Flat
Hub Collet onto each
Hub Nut. Secure them by
twisting tightly.
Pulleys
PROJECT 2: CRANE
9
10
11
13
Place two Building Block
30s on the rear end of the
crane.
Add Building Block 15
with Bore and Building
Block 7.5 on each of the
two rear end columns.
Insert Clip Axle 30 from
each of the two Building
Block 15s with Bore and
join the two Axles with an
Axle Coupling.
Place a Mounting Plate
15x45 over the two Building Block 15s with
Bore. Lock the right Clip
Axle 30 with a Clip 5.
12
13
14
Construct a handle of the
pulley with a Crank Shaft
and a Bearing Sleeve. Set
the vehicle aside.
To start the boom arm,
connect five Building
Block 30s together. On
one of the ends attach
a Building Block 15 with
Bore with the bore facing
horizontally. Insert a Clip
Axle 45 into the Building
Block 15 with Bore.
Add two Hinged Block
Claws with Bearing
Sleeves on the second
Building Block 30 from the
top.
Pulleys
PROJECT 2: CRANE
15
16
Attach the boom arm to
the central Building Block
15 with Bore with the
Hinged Block Claw facing
upwards.
Place a Building Block 30
perpendicular to another
horizontal Building Block
30. Place a Building Block
15 with Bore on the top of
the Building Block 30.
18
Tie a piece of string to
the Clip Axle 30, and loop
the string from the Clip
Axle 30 around the upper
Bearing Sleeve on the
boom arm, back down to
the first Bearing Sleeve
on the crane chassis, back
up to the lower Bearing
Sleeve on the boom arm,
and back down around
the second Bearing Sleeve
on the crane chassis and
tie it there.
Finished.
17
14
Add the beam-block
combination to the end of
the boom arm. Lock both
sides of the Clip Axle
45 with a Clip 5.
Pulleys
JOURNAL
Crane
1. Turn the Crank Shaft. Does the boom arm rise?
Yes o
No o
2. Reverse the turning direction of the Crank Shaft. Does the boom arm lower?
Yes o
No o
3. As you are turning the Crank Shaft, watch the string as it runs around the
Bearing Sleeves. Do the Bearing Sleeves turn as the string travels over them?
Yes o
No o
4. Read a definition of Block and Tackle using a dictionary or the Creya Term
Library. Define this term in your own words:
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
15
Pulleys
CHALLENGES
CHALLENGE 1
Weightlifting Challenge: Using your knowledge of pulleys, build a pulley
system capable of lifting 5 kg or more.
Hints...
Use Flat Hub Collets and Hub Nuts to create a pulley.
16
CHALLENGE 2
Extending Ladder: Pulley systems are used in many different machines. For
example, extending or telescoping ladders often have a pulley system. Use your
knowledge of pulley systems to build an extending ladder using pulleys.
Hints...
Wrap string around pulleys located at the end of the ladder support to pull the
extending part of the ladder forward.
Pulleys
JOURNAL
Challenge 1
1. Were you able to build a pulley system that could lift about 5 kg? If yes, write
a paragraph describing what you did to meet the challenge. If no, describe the
biggest problem that prevented you from succeeding at the task.
__________________________________________________________________
__________________________________________________________________
________________ __________________________________________________
__________________________________________________________________
____________ ________________ _____________________________________
__________________________________________________________________
__________________________ _______________________________________
2. Describe a situation in which a pulley system would be useful.
__________________________________________________________________
__________________________________________________________________
___________ ________________ ______________________________________
__________________________________________________________________
________________________ ________________ _________________________
__________________________________________________________________
_____________________________________ ________________ ____________
__________________________________________________________________
__________________________________________________ ________________
17
Name: _ _______________________________ Date: _____________________
Pulleys
JOURNAL
Challenge 2
1. How have you used, or planned to use, pulleys in building your extending
ladder? Sketch the model in the box provided below.
2. Describe a job or a career that may use an extending ladder.
__________________________________________________________________
__________________________________________________________________
________________ __________________________________________________
__________________________________________________________________
____________ ________________ _____________________________________
__________________________________________________________________
_________________________ ________________ ________________________
__________________________________________________________________
18
Name: _ _______________________________ Date: _____________________
Pulleys
CAPSTONE
Create a pulley system that can be used to deliver messages across the room. You may use fixed pulleys or a block and tackle and your invention may be motorized.
19
Pulleys
JOURNAL
Capstone
The design process is a systematic problem-solving strategy used to
develop possible solutions to a problem and to narrow down the possible
solutions to one choice. Several steps of the design process include answers
to the following questions:
1. DESCRIBE at least three different possible designs you could create.
These potential projects should all involve the application of a pulley
system. a. ________________________________________________________
b. ________________________________________________________
c. _________________________________________________________
Name: _ _______________________________ Date: _____________________
4. DESCRIBE your system: ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________
5. SKETCH your system:
2. CHOOSE one of the potential projects. DESCRIBE why you chose this
one:
_________________________________________________
_________________________________________________
_________________________________________________
3. CONDUCT RESEARCH on your proposed system. List three sources of
information you used:
a. ________________________________________________________
b. ________________________________________________________
c. _________________________________________________________
20
6. Describe building your model: ______________________________________________________________________
______________________________________________________________ _______
___________________________________________________________ __________
______________________________________________________________________