Pulleys
TESLA Simple Machines 2010
The Big Idea of this Investigation
A simple machine is a mechanical device that
makes work easier by magnifying, modifying,
transferring, or changing the direction of applied
force. Simple machines are the elementary
"building blocks" of which all complicated
machines are made.
Knowledge We Will Build on From Prior Investigations
Force is a push or pull applied to an object.
Work = Distance X Force
Friction is the number one enemy of simple machines. It increases the
amount of force needed to do work.
Wheels reduce the amount of friction between an object and the surface
over which it moves.
A wheel and axle can work together to magnify force and make work
easier.
ENGAGING SCENARIO
In our previous investigations we have discovered how
simple machines can make work easier by modifying or
magnifying the force applied to objects in order to complete
a task. A pulley is another simple machine that we have
not investigated that could help us raise objects to higher
locations. In this investigation we need to find out if using a
pulley to lift an object requires less force than just lifting the
object by itself.
• What is the problem we need to solve?
• What do we need to investigate?
Discuss ideas with a partner for a possible focus question.
Your focus question should be connected to what the scenario
wants us to do…
Focus Question
(What is the problem?)
How can we determine if using a pulley to lift an object
requires less force than just lifting the object by itself?
Previous Knowledge
Share experiences with pulleys related to lifting objects.
Prediction (related to the focus question)
Prediction:
I predict that _______________ because____________
If _____________________Then___________________
NOTEBOOK ENTRY
Class Predictions (related to the focus question)
New Vocabulary
Pulley
•A wheel that rotates freely around an axle. The outer rim of
most pulleys is grooved to move on a rope or chain.
Fixed Pulley:
A pulley is attached
to one location and
does not move. It is
used to move a load
up, down, or
Moveable Pulley:
A pulley that moves
with the load along
a rope or chain .
sideways.
How does the fixed pulley and the moveable pulley change the direction of
force applied in each of the models above?
Preparing the Investigation
Each group will be given a pulley, spring
scale, string, fishing line, meter stick and a
book to build your pulley system.
What are we going to
change
The way we lift the
object
No Pulley
Fixed Pulley
Moveable Pulley
What are we going to
keep the same
•The distance we lift the
object
•The object we lift
•The Spring Scale
NOTEBOOK ENTRY
Collecting Data
Do you think the amount of force required to life the object will be the same
with the fixed and moveable pulley?
Fixed Pulley
No Pulley
Trial #
Height
Force
Work
Trial #
Height
Force
(cm)
(cm)
1
1
2
2
3
3
Average 
Average 
Moveable Pulley
Trial #
Height
Force
Work
(cm)
1
2
3
Average 
NOTEBOOK ENTRY
Work
Making Meaning Conference
In which direction was force applied to lift the book:
•without the pulley?
•with the fixed pulley?
•with the moveable pulley?
How would you compare the amount of force and work
required to lift the book with these 3 methods?
What is a mechanical advantage for using the fixed pulley?
What is a mechanical advantage for using the moveable
pulley?
Would using a pulley to lift an object have other mechanical
advantages not related to force and work?
Claims and Evidence
How can we determine if using a pulley to lift an object
requires less force than just lifting the object by itself?
I claim that…
I claim this because…
NOTEBOOK ENTRY
Reflection/Conclusion
Revisit your original prediction… Explain how the evidence
did or did not support your original prediction?
My prediction was accurate because…..
I wish to revise my prediction because…
What did you learn…
What really surprised you…
What new questions do you have…
What would you like to know more about…
NOTEBOOK ENTRY