Post on 12-Mar-2018
Levers and PulleysLevers and Pulleys
55thth Grade Science Investigation Grade Science Investigation
UnitUnit
What Do We Already Know?What Do We Already Know?
�� A lever and pulley are mechanical advantages=makes A lever and pulley are mechanical advantages=makes work easier, and helps lift things you couldnwork easier, and helps lift things you couldn’’t normally t normally liftlift
�� Combined simple machines can be put together to make Combined simple machines can be put together to make compound machinescompound machines
�� Levers and pulleys are used in curtains on stagesLevers and pulleys are used in curtains on stages
�� If you have a big pulley it would help you lift something If you have a big pulley it would help you lift something on the other side.on the other side.
�� Ancient Egyptians used levers and pulleys to build the Ancient Egyptians used levers and pulleys to build the Great Pyramids.Great Pyramids.
�� Levers are in everyday things such as light switches and Levers are in everyday things such as light switches and faucets.faucets.
�� Levers balance on the fulcrumLevers balance on the fulcrum
�� Ex: Scissors?, seesaw, patio umbrellas, stick shifter in Ex: Scissors?, seesaw, patio umbrellas, stick shifter in car, car,
What Do We Already Know What Do We Already Know ‘‘0909
�� Levers are used to help you lift things Levers are used to help you lift things –– make make work easierwork easier
�� Gravity pulls down Gravity pulls down
�� Have an idea of what motion and force areHave an idea of what motion and force are
�� Levers and pulleys are both simple machinesLevers and pulleys are both simple machines
�� Simple machine: one step tools (ex. Levers)Simple machine: one step tools (ex. Levers)
�� Levers and pulleys are widely used today even Levers and pulleys are widely used today even without us realizing itwithout us realizing it
�� Use of simple machines makes work easier Use of simple machines makes work easier because it spreads the effort over a longer because it spreads the effort over a longer distancedistance
What Do We Want to Know?What Do We Want to Know?
�� Simple machine vs. compound machine?Simple machine vs. compound machine?
�� When do we get to build something?When do we get to build something?
�� Do we get to decide what we want to build?Do we get to decide what we want to build?
�� Can we build a catapult?Can we build a catapult?
�� What is a lever and pulley most commonly used What is a lever and pulley most commonly used
for?for?
�� What is the fulcrum in a lever?What is the fulcrum in a lever?
��
Investigation One: Part OneInvestigation One: Part One
�� How can a lever make work easier?How can a lever make work easier?
�� A lever is simple machine.A lever is simple machine.
�� Simple machines provide advantage to the Simple machines provide advantage to the
useruser
�� The unit used to measure the amount of The unit used to measure the amount of
force needed to lift a load or overcome a force needed to lift a load or overcome a
resistance is the Newton (N)resistance is the Newton (N)
Part 1 VocabularyPart 1 Vocabulary
�� Lever: simple machine that people use to gain a Lever: simple machine that people use to gain a mechanical advantage, such as making work mechanical advantage, such as making work easiereasier
�� Lever arm: a stick or beam free to pivot at a Lever arm: a stick or beam free to pivot at a pointpoint
�� Fulcrum: the point where the lever arm pivotsFulcrum: the point where the lever arm pivots
�� Load: the mass lifted or the resistance overcome Load: the mass lifted or the resistance overcome by a lever is the loadby a lever is the load
�� Effort: the force needed to move a load or Effort: the force needed to move a load or overcome a resistanceovercome a resistance
�� Newton: unit of measurement for forceNewton: unit of measurement for force
Inv. 1 Part 1Inv. 1 Part 1
�� Set up a lever system with the load Set up a lever system with the load
hanging at 15 cm.hanging at 15 cm.
�� Can you lift the load using only one finger?Can you lift the load using only one finger?
�� Does it always take the same amount of force Does it always take the same amount of force
to lift the load?to lift the load?
�� Where should you press to lift the load with Where should you press to lift the load with
the LEAST force?the LEAST force?
Inv. 1 Part 1Inv. 1 Part 1
�� Remove the loads from their leversRemove the loads from their levers
�� What advantage can be gained by using a What advantage can be gained by using a
lever to lift a load?lever to lift a load?
�� How can you measure the advantage How can you measure the advantage
provided by a lever?provided by a lever?
Spring ScaleSpring Scale
�� Hang the spring scale right side upHang the spring scale right side up
�� Newton is the unit used to measure force in the Newton is the unit used to measure force in the metric system, just as gram is the unit used to metric system, just as gram is the unit used to measure mass or liter is used to measure measure mass or liter is used to measure volume.volume.
�� Read the scale from the top of the metal Read the scale from the top of the metal indicatorindicator
�� Each little line on the Newton scale represents Each little line on the Newton scale represents 0.2 N. If the indicator is in between, you must 0.2 N. If the indicator is in between, you must round to the nearest 0.1 N.round to the nearest 0.1 N.
�� Stop before the scale goes past the 10Stop before the scale goes past the 10--N limit!!!!N limit!!!!
Summary of Discoveries Summary of Discoveries
�� What is the relationship between the load What is the relationship between the load
and the effort that gives a lever user (you) and the effort that gives a lever user (you)
the greatest advantage? (makes it easiest the greatest advantage? (makes it easiest
to lift the load?)to lift the load?)
Summary of DiscoverySummary of Discovery
�� When the effort is applied at a great When the effort is applied at a great
distance from the fulcrum, the load is easy distance from the fulcrum, the load is easy
to liftto lift
Part One : In ConclusionPart One : In Conclusion
�� A lever can make a load easier to lift, it A lever can make a load easier to lift, it
can move loads, and it reduces the effort.can move loads, and it reduces the effort.
�� In a lever system the farther from the In a lever system the farther from the
fulcrum the effort is applied, the greater fulcrum the effort is applied, the greater
the advantage to the lever user.the advantage to the lever user.
Investigation 1: Part 2Investigation 1: Part 2Lever Experiment ALever Experiment A
�� You will need:You will need:
�� No. 4 Student Sheet (Lever Experiment A No. 4 Student Sheet (Lever Experiment A
Graph)Graph)
�� No. 5 Student Sheet (Response Sheet No. 5 Student Sheet (Response Sheet ––
Levers)Levers)
�� Find your science group from FridayFind your science group from Friday
Lift the LoadLift the Load
�� How much force (effort) is needed to lift How much force (effort) is needed to lift
the load?the load?
�� A scale is useful tool for measuring the A scale is useful tool for measuring the
amount of force needed to lift a load. amount of force needed to lift a load.
Force is always measured in Force is always measured in newtonsnewtons..
Student SheetStudent Sheet
�� Lever Experiment ALever Experiment A
�� The load stays at 10 cm, and the effort is The load stays at 10 cm, and the effort is
applied at various distances from the applied at various distances from the
fulcrum (5 cm intervals except for the first fulcrum (5 cm intervals except for the first
(2.5 cm))(2.5 cm))
The Force of the ScaleThe Force of the Scale
�� Put the load 5 cm from the fulcrumPut the load 5 cm from the fulcrum
�� Put the scales 25 cm from the fulcrum on the Put the scales 25 cm from the fulcrum on the
other sideother side
�� The load is 5 cm from the fulcrum. How much The load is 5 cm from the fulcrum. How much
pull is being applied to lift the load?pull is being applied to lift the load?
�� The load is being lifted with no effort. How is The load is being lifted with no effort. How is
that possible?that possible?
�� If the weight of the scale is lifting the load, how If the weight of the scale is lifting the load, how
can we find out how many can we find out how many newtonsnewtons that is?that is?
VocabularyVocabulary
�� TwoTwo--coordinate graphs: shows coordinate graphs: shows
relationships between two variablesrelationships between two variables
�� Advantage: a benefit obtained by using a Advantage: a benefit obtained by using a
lever (or other simple machine)lever (or other simple machine)
Inv. 1 Part 2: New UnderstandingInv. 1 Part 2: New Understanding
�� When the load is at a constant position on the When the load is at a constant position on the lever arm, how can you make it easier to lift the lever arm, how can you make it easier to lift the load?load?�� The farther the effort is from the fulcrum, the easier it The farther the effort is from the fulcrum, the easier it is to lift the load.is to lift the load.
�� What is the difference between the weight of What is the difference between the weight of the load and the amount of effort needed to lift the load and the amount of effort needed to lift it?it?�� The weight of the load remains constant; the effort The weight of the load remains constant; the effort needed to lift the load varies depending on where the needed to lift the load varies depending on where the effort is applied on the lever arm.effort is applied on the lever arm.
a
Inv. 1 Part 3Inv. 1 Part 3
�� You will need:You will need:
�� Materials for lever experiment (same as for Materials for lever experiment (same as for
part 2)part 2)
�� Student Sheet no. 6 Lever Experiment BStudent Sheet no. 6 Lever Experiment B
Propose Reversing the ExperimentPropose Reversing the Experiment
�� What do you think would happen to the What do you think would happen to the
effort needed to lift the load ifeffort needed to lift the load if
a.a. the scale stayed at one location on the the scale stayed at one location on the
lever, andlever, and
b.b. The The loadload moved farther and farther from moved farther and farther from
the fulcrumthe fulcrum
Would the results be the same as moving the Would the results be the same as moving the
location of the effort?location of the effort?
LetLet’’s Begin Lever Experiment B!s Begin Lever Experiment B!
�� The scale must stay at 10 cm on your The scale must stay at 10 cm on your
lever and the LOAD will move this time.lever and the LOAD will move this time.
TwoTwo--Coordinate GraphCoordinate Graph
�� Graph your results from Experiment BGraph your results from Experiment B
�� PLEASE NOTE:PLEASE NOTE:
�� XX--axis: independent variable (what YOU axis: independent variable (what YOU
changed during the experiment)changed during the experiment)
�� YY--axis: dependent variable (what you found axis: dependent variable (what you found
out)out)
LetLet’’s Discuss Our Results!s Discuss Our Results!
�� How does your graph of experiment A How does your graph of experiment A
compare to your graph from experiment Bcompare to your graph from experiment B
�� The graph of experiment B starts at (0,0) and The graph of experiment B starts at (0,0) and
is a straight inclined line is a straight inclined line --or it should or it should
bebe………….. : ).. : )
LetLet’’s Discuss Our Results!s Discuss Our Results!
�� What is the relationship between the What is the relationship between the
location of the load on the lever system location of the load on the lever system
and the effort it takes to move it?and the effort it takes to move it?
�� The effort needed to lift the load decreases as The effort needed to lift the load decreases as
the load gets closer to the fulcrum; the effort the load gets closer to the fulcrum; the effort
increases as the load gets farther from the increases as the load gets farther from the
fulcrumfulcrum
Investigation 1 QuizInvestigation 1 Quiz1.1. What is the difference between Lever What is the difference between Lever
Experiment A and Lever Experiment B?Experiment A and Lever Experiment B?
2.2. What do both the experiments help us What do both the experiments help us
understand about levers?understand about levers?
3.3. In a twoIn a two--coordinate graph, do you place the coordinate graph, do you place the
independent variable on the horizontal line independent variable on the horizontal line
(x(x--axis) or the vertical (yaxis) or the vertical (y--axis)?axis)?
4.4. What is a fulcrum?What is a fulcrum?
5.5. What is advantage in simple machines? What is advantage in simple machines?
�� Review LeversReview Levers
�� Consider the Force of the LoadConsider the Force of the Load
�� Remember, a force is a push or a pull. When Remember, a force is a push or a pull. When
the load hangs on the lever or the spring the load hangs on the lever or the spring
scale, it pulls down with a force. The load we scale, it pulls down with a force. The load we
use pulls with a force of 2.4 Nuse pulls with a force of 2.4 N
�� Set Up a Demonstration LeverSet Up a Demonstration Lever
�� Place the load at 20 cmPlace the load at 20 cm
�� Will the effort needed to lift the load be more, Will the effort needed to lift the load be more,
less, or the same as the pull of the load?less, or the same as the pull of the load?
�� Move the FulcrumMove the Fulcrum
�� This lever has the fulcrum right in the middle This lever has the fulcrum right in the middle
of the lever arm. Is the fulcrum always right of the lever arm. Is the fulcrum always right
in the middle of the lever arm?in the middle of the lever arm?
�� What might happen if the fulcrum was not in What might happen if the fulcrum was not in
the middle? Would it still be a lever?the middle? Would it still be a lever?
�� Is there any advantage to moving the fulcrum Is there any advantage to moving the fulcrum
to new locations along the lever arm?to new locations along the lever arm?
�� Form into your teamsForm into your teams
�� GETTERS get the materials they need for GETTERS get the materials they need for
two lever systems.two lever systems.
�� Experiment!Experiment!
�� What did you find out?What did you find out?
Class 1 LeversClass 1 Levers
�� You have been working with CLASS 1 You have been working with CLASS 1
LEVER SYSTEMS. Class 1 Lever Systems LEVER SYSTEMS. Class 1 Lever Systems
always have the fulcrum somewhere always have the fulcrum somewhere
between the load and the effort.between the load and the effort.
Other ArrangementsOther Arrangements
�� Can there be other arrangements of the Can there be other arrangements of the
load, effort, and fulcrum?load, effort, and fulcrum?
�� The load in the middle?The load in the middle?
�� The effort in the middle?The effort in the middle?
New Levers?!New Levers?!
�� Investigate New Levers!Investigate New Levers!
�� Work with your team to see if you can set up Work with your team to see if you can set up
a different kind of lever system. Try to find a different kind of lever system. Try to find
out what kind of advantage (if any) it out what kind of advantage (if any) it
provides.provides.
Did You Discover Different Levers?Did You Discover Different Levers?
�� ClassClass--1 Levers:1 Levers: Levers with the fulcrum Levers with the fulcrum in the middle and load in the middle and load and effort at the endsand effort at the ends
�� ClassClass--2 Levers:2 Levers: Levers with the load in Levers with the load in the middle and the the middle and the fulcrum and effort at the fulcrum and effort at the endsends
�� ClassClass--3 Levers:3 Levers: Levers with the effort in Levers with the effort in the middle and the the middle and the fulcrum and load at the fulcrum and load at the endsends
LetLet’’s Practice Setting Up Three s Practice Setting Up Three Classes of Levers!Classes of Levers!
�� Try to set up each of the three typesTry to set up each of the three types
�� Mnemonic Device: FLEMnemonic Device: FLE——11--22--33�� The FLE stands for the part of the lever The FLE stands for the part of the lever system that is in the middle of the leversystem that is in the middle of the lever
�� ItIt’’s as easy as FLEs as easy as FLE——11--22--3!3!
�� Bottom Line: Levers can be set up in three Bottom Line: Levers can be set up in three basic ways. They are called class 1, class basic ways. They are called class 1, class 2, and class 3.2, and class 3.
Investigation Two: Part TwoInvestigation Two: Part TwoLever DiagramsLever Diagrams
�� DiagramDiagram�� A drawing that explains the relationship of the A drawing that explains the relationship of the parts of the system, in this case a lever parts of the system, in this case a lever systemsystem
�� A diagram uses a system of symbols and A diagram uses a system of symbols and conventions to communicate information conventions to communicate information about lever designs.about lever designs.
Investigation TwoInvestigation TwoPart Three: RealPart Three: Real--World LeversWorld Levers
�� We will need:We will need:�� Student Sheet no. 12 called Student Sheet no. 12 called ““Levers at WorkLevers at Work””
�� 1 broom1 broom
�� 1 nutcracker1 nutcracker
�� 1 scissors1 scissors
�� 1 bottle opener1 bottle opener
�� 1 pliers1 pliers
�� 1 tweezers1 tweezers
�� 1 hammer1 hammer
�� Half meter sticksHalf meter sticks
�� Loads with rubber bandsLoads with rubber bands
�� Masking tapeMasking tape
�� 3 lever diagrams and 3 lever pictures (on bulletin board)3 lever diagrams and 3 lever pictures (on bulletin board)
RealReal--World LeversWorld Levers
�� Levers are all around us in the world Levers are all around us in the world ––
every toolbox, kitchen drawer, toys, every toolbox, kitchen drawer, toys,
appliances, cars, and machines.appliances, cars, and machines.
�� LetLet’’s review each of the three types of s review each of the three types of
leverslevers…………..
Levers at WorkLevers at Work
�� We have a number of tools here to We have a number of tools here to investigate. Each one uses one or more investigate. Each one uses one or more levers to give its user some kind of levers to give its user some kind of advantageadvantage�� Investigate each toolInvestigate each tool
�� Analyze it to kind the leversAnalyze it to kind the levers
�� Diagram it on the levers at work student Diagram it on the levers at work student sheetsheet
�� Write the leverWrite the lever’’s class on the sheet in the s class on the sheet in the space providedspace provided
Levers at WorkLevers at Work
�� LetLet’’s try one together:s try one together:
�� What class of lever is the screwdriver when it is used What class of lever is the screwdriver when it is used
to pry the lid off a can? (Class 1)to pry the lid off a can? (Class 1)
�� When you are trying to lift the lid off a can of putty or When you are trying to lift the lid off a can of putty or
paint, there is no metal cube to be lifted. Where is paint, there is no metal cube to be lifted. Where is
the load, and what direction is the load acting?the load, and what direction is the load acting?
�� Load can be either a mass that you lift or a resistance that Load can be either a mass that you lift or a resistance that
you need to overcome. Here the resistance is the load.you need to overcome. Here the resistance is the load.
�� Identify the load, fulcrum, effort, and class. Identify the load, fulcrum, effort, and class.
�� Diagram the leverDiagram the lever
Report the ResultsReport the Results
�� Each team report on one of the tools, Each team report on one of the tools,
identifying its class and diagramming the identifying its class and diagramming the
lever on the board.lever on the board.
Wrapping Up Part 3Wrapping Up Part 3
�� VocabVocab
�� New Concepts New Concepts –– Part ThreePart Three
�� Many common tools use levers: scissors, Many common tools use levers: scissors,
pliers, bottle openers, hammers, pliers, bottle openers, hammers,
wheelbarrows, and brooms, to name a few.wheelbarrows, and brooms, to name a few.
�� Effort is reduced as the load moves closer to Effort is reduced as the load moves closer to
the fulcrumthe fulcrum
�� LetLet’’s read Science Stories: Classs read Science Stories: Class--3 Levers!!3 Levers!!
Investigation ThreeInvestigation ThreePart Four: Lever PicturesPart Four: Lever Pictures
�� We will need:We will need:
Part One:Part One:OneOne--Pulley SystemsPulley Systems
�� Inquiry Questions:Inquiry Questions:
�� How much effort is needed to lift a load in a How much effort is needed to lift a load in a
oneone--pulley system?pulley system?
�� Is it always the same?Is it always the same?
Part One:Part One:OneOne--Pulley SystemsPulley Systems
�� If you were on a construction site and If you were on a construction site and
needed to lift a steel grinder to the fifth needed to lift a steel grinder to the fifth
floor of a building, you would need the floor of a building, you would need the
worldworld’’s biggest lever. Not very practical! s biggest lever. Not very practical!
Levers do provide advantage, but they Levers do provide advantage, but they
arenaren’’t appropriate for certain jobs. It t appropriate for certain jobs. It
would make more sense to use a pulley.would make more sense to use a pulley.
Free Exploration with One PulleyFree Exploration with One Pulley
�� Find out if you can use a pulleyFind out if you can use a pulley
�� Can a pulley be used to lift a load?Can a pulley be used to lift a load?
Scientific MethodScientific Method
�� LetLet’’s organize this experiment based on s organize this experiment based on
the scientific method.the scientific method.
�� What is the order of the scientific method?What is the order of the scientific method?
�� What is the independent variable of this What is the independent variable of this
experiment? experiment?
�� What is the dependent variable?What is the dependent variable?
�� What is the control variable?What is the control variable?
�� What is the testable question?What is the testable question?
�� Can we form a hypothesis statement?Can we form a hypothesis statement?
Name the PulleyName the Pulley
�� Pulley: a wheel with a grooved rim in Pulley: a wheel with a grooved rim in which a rope can run to change the which a rope can run to change the direction of the pull (force) that lifts the direction of the pull (force) that lifts the loadload
�� Fixed pulley: has a wheel that is Fixed pulley: has a wheel that is attached/secured to something above the attached/secured to something above the pulley (meter stick in this case)pulley (meter stick in this case)
�� Movable pulley: has a wheel that is Movable pulley: has a wheel that is attached to the loadattached to the load
�� Mechanical advantageMechanical advantage: reduces the : reduces the
effort (force) needed to lift a load or effort (force) needed to lift a load or
overcome a resistance; it results from overcome a resistance; it results from
using a simple machine.using a simple machine.
�� Directional advantageDirectional advantage: is a change in : is a change in
direction that results from passing a rope direction that results from passing a rope
through a pulleythrough a pulley
Inquiry AnsweredInquiry Answered
�� Can a pulley be used to lift a load?Can a pulley be used to lift a load?
�� A single pulley can be set up as a fixed pulley A single pulley can be set up as a fixed pulley
or a movable pulley to lift a loador a movable pulley to lift a load
�� Do singleDo single--pulley systems provide pulley systems provide
advantage?advantage?
�� SingleSingle--fixed pulleys change the direction of fixed pulleys change the direction of
effort. (directional advantage)effort. (directional advantage)
�� SingleSingle--movable pulleys reduce the effort movable pulleys reduce the effort
needed to lift the load. (mechanical needed to lift the load. (mechanical
advantage)advantage)
Part one continuedPart one continued……..
�� Pulley Diagrams Student SheetPulley Diagrams Student Sheet
�� Spring ScalesSpring Scales
�� Zero the scales at the beginning of every Zero the scales at the beginning of every
sessionsession
�� Always use the spring scales right side upAlways use the spring scales right side up
�� Add 0.5 N to scale readings only when pulling Add 0.5 N to scale readings only when pulling
downdown
SingleSingle--
movablemovable
SingleSingle--
fixedfixed
Effort Effort
(N)(N)Scale Scale
reading reading
(N)(N)
Direction Direction
of Pull of Pull
(Draw (Draw
arrow)arrow)
Load (N)Load (N)Pulley Pulley
SystemSystem
LetLet’’s Review the Ones Review the One--Pulley Pulley SystemsSystems……
�� How are fixed and movable pulleys the How are fixed and movable pulleys the
same?same?
�� What kind of advantage is provided by What kind of advantage is provided by
each pulley system?each pulley system?
�� In what ways are pulleys and levers the In what ways are pulleys and levers the
same?same?
The TwoThe Two--Pulley ChallengePulley Challenge
�� Is there any advantage to using two Is there any advantage to using two
pulleys at the same time?pulleys at the same time?
�� LetLet’’s break into our science groups and s break into our science groups and
give it a try!give it a try!
�� I might give you a hint in a few I might give you a hint in a few
minutesminutes………………
Keep the Wheels TurningKeep the Wheels Turning
�� Pulley Diagrams Student Sheet againPulley Diagrams Student Sheet again
�� LetLet’’s diagram the pulleys using red dot s diagram the pulleys using red dot
stickersstickers
Part Two: Inquiry AnsweredPart Two: Inquiry Answered
Is there any advantage to using two pulleys Is there any advantage to using two pulleys
at the same time?at the same time?
�� Two pulleys can provide greater mechanical Two pulleys can provide greater mechanical
advantage than one when lifting loads.advantage than one when lifting loads.
What is a simple machine?What is a simple machine?
�� Simple machines provide mechanical or other Simple machines provide mechanical or other
advantage.advantage.
Response Sheet Response Sheet -- PulleysPulleys
�� What type of pulley did he use?What type of pulley did he use?
�� Single movable Single movable
�� How do you know?How do you know?
�� What would the pulley look like?What would the pulley look like?
�� How much easier do you think this made How much easier do you think this made
the work of lifting the load?the work of lifting the load?
�� It took half as much effort as the weight of It took half as much effort as the weight of
the loadthe load
�� How do you know?How do you know?
Unit ReviewUnit Review�� Utilize all of your notes in your portfolioUtilize all of your notes in your portfolio
�� Go over content questions and answers from Go over content questions and answers from each investigationeach investigation
�� Utilize previous quizzes from the unitUtilize previous quizzes from the unit
�� What is the purpose of a lever?What is the purpose of a lever?
�� Be able to diagram different leversBe able to diagram different levers
�� Be able to identify different leversBe able to identify different levers
�� What is the purpose of a pulley system?What is the purpose of a pulley system?
�� Be able to diagram different pulley systemsBe able to diagram different pulley systems
�� What do simple machines offer the user?What do simple machines offer the user?
�� Be sure to review the study guide that was Be sure to review the study guide that was handed out on Fridayhanded out on Friday