Activity Objectives: view - Marc Small - Teaching...

2005 PROTOTYPE Positively Aging®/M.O.R.E.2004©The University of Texas Health Science Center at San Antonio 1

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LESSON 2 ACTIVITY 2A

Just a little Bit of Effort:Exploring LeversActivity 2AActivity Objectives:By setting up levers and measuring forces, students will be able to:

u Name and define the parts of a leveru Describe the location of the fulcrum, effort and resistance in each

class of leveru Investigate the forces involved in each class of leveru Draw conclusions regarding appropriate application of each

class of lever

Activity Description:Students will explore the parts of a lever and will build a model of eachclass of lever on a wooden stand using dowels and modified woodenrulers. Using a spring scale and hanging weights, students will study theforces and will determine the advantage of each type of lever. As agrand finale to the activity, students will apply their newly foundknowledge of levers as they compete in a contest called the “Little Bit of Effort Contest.” Students will work in their groups to design the mostefficient lever in each class, ie the lever that can move the most weightwith the least amount of effort.

Activity Background:A lever is a rigid bar moving about a fixed point (fulcrum). More specifi-cally, a lever consists of an effort force, resistance force, rigid bar and afulcrum. The effort in a lever is a force applied to the lever in a specific direction and will cause movement in the lever if not balanced by an opposing force. The resistance*in a lever is the force that opposes the effort force. The fulcrum in a lever is the support around which the lever pivots. Levers are classified according to the position of the fulcrum, resistance (load), and effort relative to each other. The combination of these relative locations results in first class, second class and third class levers.

* Resistance is also called “Load”

First class lever (EFR) - The Effort (E) and Resistance (R) are located onopposite sides of fulcrum as shown in Figure 1: First Class Lever below.Examples of a first class lever include pry bars, see saws, crowbars.

Figure 1 First Class Lever

Second Class lever (FRE) - The Effort (E) and the Resistance (R) arelocated on the same side of fulcrum and the Resistance (R) is betweenfulcrum and Effort (E) as shown in Figure 2, Second Class Lever below.An example of a second class lever is a wheelbarrow.

Figure 2 Second Class Lever

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Third class lever (FER) - The Effort (E) and Resistance (R) are located on the same side of fulcrum, but the Effort (E) acts between fulcrum andthe Resistance (R) as shown in Figure 3 Third Class Lever. Examples of athird class lever include a shovel and a broom. A large effort gains speedof motion in this type of lever. It is the most common lever type in thehuman body.

Figure 3 Third Class Lever

Activity Materials: (per group)• Copy of Student Activity Page Packet• 1 Copy of Student Data Page Packet per student• Wooden stand with hook inserted• Wooden ruler • 3 Binder clips 1 1/4” wide, 5/8” capacity• Hanging weight set• Spring scale – measurement scale needs to match that of hanging

weight set• Certificates for “Little Bit of Effort” Contest


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Activity Management Suggestions:Students should work in groups of two to four. Remind students to

use good time management skills and to divide the jobs equally so everymember of the group has a fair share of the tasks.

During the “processing out” time, be sure that students have discov-ered the unexpected result related to third class levers. Students expectto find that each lever will reduce the amount of force needed to movean object and will be surprised to find that the third class lever actuallyhas a mechanical disadvantage. This concept will be important for students as they progress to the next activity on biomechanics of leversin the human body.

Extension:Students can collect household tools and determine which type of leverthey represent.

Activity References Used:Broer, MR. (1973) Efficiency of human movement (Third Edition).Philadelphia: W.B. Saunders Company.

Gowitzke, BA & Milner, M. (1988). Scientific bases of human movement(Third Edition). Baltimore: Williams & Wilkins.

Gray, H. (1918). Anatomy of the human body (20th Edition).Philadelphia: Lea & Febiger.

Hamill, J. & Knutzen, KM. (2003). Biomechanical basis of human move-ment (Second Edition). New York: Lippincott Williams & Wilkins.

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Previous learningassumed:

Concept of Force, Use of spring scale,

Group skills, following directions

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Relevant TEKS:6.1 A The student conducts field and laboratory investigations using safe, environmentally appropriate, andethical practices. The student is expected to demonstratesafe practices during field and laboratory investigations6.2 The student uses scientific inquiry methods duringfield and laboratory investigations. The student is expectedto: (B) collect data by observing and measuring; (C) analyze and interpret information to construct reasonable explanations from direct and indirect evidence; (D) communicate valid conclusions; and(E) construct graphs, tables, maps, and charts using toolsincluding computers to organize, examine, and evaluatedata. 6.4 The student knows how to use a variety of tools andmethods to conduct science inquiry. The student is expectedto: (A) collect, analyze, and record information using toolsincluding beakers, petri dishes, meter sticks, graduatedcylinders, weather instruments, timing devices, hot plates,test tubes, safety goggles, spring scales, magnets, balances,microscopes, telescopes, thermometers, calculators, fieldequipment, compasses, computers, and computer probes;7.1 Scientific processes. The student conducts field and lab-oratory investigations using safe, environmentally appropri-ate, and ethical practices. The student is expected to: (A) demonstrate safe practices during field and laboratoryinvestigations7.2 Scientific processes. The student uses scientific inquirymethods during field and laboratory investigations. The student is expected to: (B) collect data by observing and measuring; (C) organize, analyze, make inferences, and predict trendsfrom direct and indirect evidence; (D) communicate valid conclusions; and(E) construct graphs, tables, maps, and charts using toolsincluding computers to organize, examine, and evaluatedata. 7.4 Scientific processes. The student knows how to use toolsand methods to conduct science inquiry. The student isexpected to: (A) collect, analyze, and record information to explain aphenomenon using tools including beakers, petri dishes,meter sticks, graduated cylinders, weather instruments, hotplates, dissecting equipment, test tubes, safety goggles,spring scales, balances, microscopes, telescopes, thermome-ters, calculators, field equipment, computers, computerprobes, timing devices, magnets, and compasses7.6 The student knows that there is a relationship betweenforce and motion. The student is expected to: (A) demonstrate basic relationships between force andmotion using simple machines including pulleys and levers8.1 The student conducts field and laboratory investiga-tions using safe, environmentally appropriate, and ethicalpractices. The student is expected to: (A) demonstrate safe practices during field and laboratoryinvestigations8.2 The student uses scientific inquiry methods during fieldand laboratory investigations. The student is expected to: (B) collect data by observing and measuring; (C) organize, analyze, evaluate, make inferences, and predict trends from direct and indirect evidence; (D) communicate valid conclusions; and(E) construct graphs, tables, maps, and charts using toolsincluding computers to organize, examine, and evaluatedata. 8.4 The student knows how to use a variety of tools andmethods to conduct science inquiry. The student is expectedto: (A) collect, record, and analyze information using toolsincluding beakers, petri dishes, meter sticks, graduatedcylinders, weather instruments, hot plates, dissecting equipment, test tubes, safety goggles, spring scales, balances, microscopes, telescopes, thermometers, calculators, field equipment, computers, computer probes,water test kits, and timing devices

Activity “Administrivia”:

Intended Grade Level:

6-8Key Concepts:

Classes of levers, Forces at work in each

class of lever

Process Skills utilized in Activity:

Observing, Inferring,

Measuring

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Just a Little Bit of Effort: Exploring Levers

Student Activity Page 2A

Activity Introduction:How many times have you used a broom, rake, pair of pliers, wheelbarrow, pry bar or played on a see saw? Each of these items involves a simple machine; the lever. Simple machines are designed to make work easier in some way, so they are goodto have around!

Activity Background:A lever is a rigid bar moving about a fixed point (fulcrum). More specifically, a lever consists of an effort force, resistance force (also called load) , rigid bar and a fulcrum. The effort in alever is a force applied to the lever in a specific direction and will cause movement in thelever if not balanced by an opposing force. The resistance in a lever is the force that opposesthe effort force. The fulcrum in a lever is the support around which the lever pivots. Leversare classified according to the position of the fulcrum, resistance, and effort relative to eachother. The combination of these relative locations results in first class, second class and third class levers.

First class lever (EFR)- The Effort (E) and Resistance (R) are located on opposite sides of fulcrum as shown in Figure 1: First Class Lever below. Examples of a first class lever includepry bars, see saws, crowbars.

Figure 1 First Class Lever


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Second Class lever (FRE) - The Effort (E) and the Resistance (R) are located on the same side of fulcrum and the Resistance (R) is between fulcrum and Effort (E) as shown in Figure 2, Second Class Lever below. An example of a second class lever is a wheelbarrow.

Figure 2 Second Class Lever

Third class lever (FER) - The Effort (E) and Resistance (R) are located on the same side offulcrum, but the Effort (E) acts between fulcrum and the Resistance (R) as shown in Figure 3Third Class Lever shown below. Examples of a third class lever include a shovel and a broom.Large effort gains speed of motion in this type of lever. It is the most common lever type inthe human body.

Figure 3 Third Class Lever Dis

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LESSON 2 ACTIVITY 2A2005 PROTOTYPE

Positively Aging®/M.O.R.E.2004©The University of Texas Health Science Center at San Antonio 8

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Activity Materials: (per group)• Copy of Student Activity Page Packet• 1 Copy of Student Data Page Packet per student• Wooden stand with hook inserted• Wooden ruler • 3 Binder clips 1 1/4” wide, 5/8” capacity• Hanging weight set• Spring scale – measurement scale needs to match that of hanging weight set

Instructions: (Read each instruction and check off each step as it is completed.)

1. Observe the diagrams of each class of lever in the background on this Student Activity Page. Be sure you can define each part of a lever and that you can describe how each class of lever is constructed.

2. First Class Levers

p a. Using the wooden stand with hook and wooden ruler, construct a first class lever. Place one binder clip onto the ruler so it will hang at its’ center point on the hook of the wooden stand. Attach a second binder clip so it is centered over the 2 cm mark on the wooden ruler. Place a 1 N weight so that it hangs from a third binder clip placed at 28 cm on the wooden ruler. See Figure 1 Constructing a First Class Lever.

Figure 1 Constructing a First Class Leverp b. Pull on the spring scale until the wooden ruler is level; the lever now is balanced

and is in equilibrium.

p c. Read the force you are applying (Effort) in Newtons on the spring scale and record it in Table 1, Exploring First Class Levers on your Student Data Page.

p d. Repeat steps a – c placing the hanging weight (Resistance) at 4 cm and the spring scale to measure the Effort in Newtons at 28 cm.

p e. Repeat steps a – c, using the locations for the Effort and Resistance providedin Table 1, Exploring First Class Levers. Record your measurements in Table 1, Exploring First Class Levers on your Student Data Page.

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ÔSPRING SCALE

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Pull up to measureforce required to balance

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3. Second Class Levers

p a. Create a second class lever on the wooden stand. Place the fulcrum at 2 cm, the hanging weight (Resistance) at 6 cm and the spring scale to measure the Effort force in Newtons at 28 cm. Balance the lever so the wooden ruler is level and read the amount of force you are

exerting to keep the lever in equilibrium. Record this information in Table 2 Exploring in a Second Class Levers.

p b. Repeat step a using the locations for the Resistance and Effort and recording the data in Table 2 Exploring Second Class Levers.

4. Third Class Levers

p a. Create a third class lever on the wooden stand. Place the fulcrum at 2 cm, the hanging weight (Resistance) at 6 cm and the spring scale to measure the Effort force in Newtons at 28 cm. Pull on the spring scale to balance the lever so that the ruler is level and thus in equilibrium. Read the amount of force you are exerting to keep the lever in equilibrium and record all data in Table 3 Exploring Third Class Levers.

p b. Repeat step a using the other locations for the Resistance and Effort and recording the data in Table 3 Exploring Third Class Levers.

5. The Great “Little Bit of Effort” Contest

p a. After you have explored the three classes of levers and have “processed out” the information to be sure you understand levers, you are ready to enter The Great “Little Bit of Effort” Contest.

p b. In this contest, you and your group members will apply what you have learned about levers and will design a first class lever that can move the greatest amount of weight with the least amount of effort.

p c. When you are ready for the judging, raise your hand so your teacher can come to your work area and verify the results. While you are waiting for the teacher to verify your results, make a drawing of your lever design on the contest entry form.Be sure to label the fulcrum, effort and resistance and label the locations of each in cm.

p d. Repeat steps b – c for your second class lever design.

p e. Repeat steps b – c for your third class lever design.

p f. When you finish with all three parts of the contest, you will complete Table 4, “The Little Bit of Effort” Contest, including calculating the ratio of Resistance Force ÷ Effort Force for each class of levers you design. The ratio you calculate is called the mechanical advantage of your lever system.

p g. When you finish Table 4, fill out the “Little Bit of Effort” Contest Entry Form and wait for the results!

Just a Little Bit of Effort: Exploring LeversStudent Activity 2A

Data Sheet

I. Exploring First Class Levers

Table 1 Exploring First Class Levers

Processing Out:1. Draw the first set up of your first class lever. Be sure to label the fulcrum, effort and

resistance and the location of each in cm.

2. How much effort did it take to lift the resistance of 1 N when the effort and the resistancewere the same distance from the fulcrum? _________________________________________

3. Would this arrangement make your work less if you had to move a heavy object? Why or why not? __________________________________________________________________________________________________________________________________________________________________________________________________


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Location of Effort

(cm)

31351061239

Distance BetweenFulcrum and Effort (cm)

Effort Force (N)

Location of

Resistance(cm)

13810512 693

Distance BetweenResistance andFulcrum (cm)

Resistance Force (N)

4. As the resistance was moved closer to the fulcrum, and the effort was left in the same location, what happened to the amount of effort needed to counter-balance the resistance? ________________________________________________________________________________________________________________________________________________________________________________________________

5. When you moved the resistance and effort as described in question 3, did the move make this lever more efficient? Why or why not? ______________________________________________________________________________________________________________________________________________________________

6. Look at your data in Table 1 Exploring First Class Levers. When the Resistance was further from the fulcrum than the Effort, what happened to the amount of Effort required to balance the resistance? ______________________________________________________________________________________________________________________________________________________________

7. What is the effect of distance from the fulcrum on this lever system? (Be sure to discuss both Resistance (load) and Effort.) ______________________________________________________________________________________________________________________________________________________________

II. Exploring Second Class Levers (Put the fulcrum at 2cm)

Table 2 Exploring Second Class Levers


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2828282018152025


Effort Force (N)

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681066 61015




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Processing Out:1. Draw the first set up of your second class lever. Be sure to label the fulcrum,

effort and resistance and the location of each in cm.

2. How much effort did it take to lift the resistance of 1 N in the first set up of this lever? ______________________________________________________

3. Would this arrangement make your work less if you had to move a heavy object? Why or why not? ______________________________________________________________________________________________________________________________________________________________

4. When the resistance was moved closer to the fulcrum, and the effort stayed in the same location, what happened to the amount of effort needed to counterbalance the resistance? ______________________________________________________________________________________________________________________________________________________________

5. When you moved the resistance and effort as described in question 3, did the move makethis lever more efficient? Why or why not? _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

6. Look at your data in Table 2 Exploring Second Class Levers. When the Resistance was further from the fulcrum and the location of the effort stayed the same, what happened to the amount of Effort required to counterbalance the resistance? ______________________________________________________________________________________________________________________________________________________________

7. What is the effect of distance from the fulcrum on this lever system? Be sure to discuss both Resistance (load) and Effort).__________________________________________________________________________________________________________________________________________


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LESSON 2ACTIVITY 2A

III. Exploring Third Class Levers (Put the fulcrum at 2cm)

Table 3 Exploring Third Class Levers

Processing Out:1. Draw the first set up of your third class lever. Be sure to label the fulcrum, effort and

resistance and the location of each in cm.

2. How much effort did it take to lift the resistance of 1 N in the first set up of this lever? _______________________________________________________________________________

3. Would this arrangement make your work less if you had to move a heavy object? Why or why not? ______________________________________________________________________________________________________________________________________________________________

Location of Effort

(cm)

15101010151066


Effort Force (N)

Location of

Resistance(cm)

2828282018 152025




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4. When the resistance was moved closer to the fulcrum, and the effort stayed in the same location, what happened to the amount of effort needed to counter-balance the resistance? ________________________________________________________________________________________________________________________________________________________________________________________________

5. When you moved the resistance and effort as described in question 3, did the move make this lever more efficient? Why or why not? _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

6. Look at your data in Table 3 Exploring Third Class Levers. When the Resistance was further from the fulcrum and the location of the effort stayed the same, what happened to the amount of Effort required to counterbalance the resistance? _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

7. What is the effect of distance from the fulcrum on this lever system? (Be sure to discuss both Resistance (Load) and Effort). ______________________________________________________________________________________________________________________________________________________________

8. What unexpected results did you find when you worked with the third class lever? ______________________________________________________________________________________________________________________________________________________________


IV. The Little Bit of Effort Contest Contest

Table 4 “Little Bit of Effort” Contest (Ratio of Resistance/Effort)

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EFFORTForce (N)

RESISTANCEForce (N)

EFFORTForce (N)

RESISTANCEForce (N)

EFFORTForce (N)

RESISTANCEForce (N)

FIRST CLASS SECOND CLASS THIRD CLASS

“Little Bit of Effort” Contest Entry Form

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Name(s) _________________________________________________________________________________________

Activity Objectives: view - Marc Small - Teaching...

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