Activity Overview. Just a little Bit of Effort: Exploring Levers Activity 2A. Discrepant Design. Activity Objectives: LESSON 2

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1 Just a little Bit of ffort: xploring Levers Activity Activity Objectives: By setting up levers and measuring forces, students will be able to: Name and define the parts of a lever Describe the location of the fulcrum, effort and resistance in each class of lever Investigate the forces involved in each class of lever 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 each class of lever on a wooden stand using dowels and modified wooden rulers. Using a spring scale and hanging weights, students will study the forces and will determine the advantage of each type of lever. As a grand finale to the activity, students will apply their newly found knowledge of levers as they compete in a contest called the Little Bit of ffort Contest. Students will work in their groups to design the most efficient lever in each class, ie the lever that can move the most weight with the least amount of effort. 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, rigid bar and a fulcrum. 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. * esistance is also called Load Activity Overview 2004 The University of Texas Health Science Center at San Antonio 1

2 First class lever (F) - The ffort () and esistance () are located on opposite sides of fulcrum as shown in Figure 1: First Class Lever below. xamples of a first class lever include pry bars, see saws, crowbars. Figure 1 First Class Lever Second Class lever (F) - The ffort () and the esistance () are located on the same side of fulcrum and the esistance () is between fulcrum and ffort () as shown in Figure 2, Second Class Lever below. An example of a second class lever is a wheelbarrow. Figure 2 Second Class Lever 2004 The University of Texas Health Science Center at San Antonio 2 Activity Overview Continued

3 Third class lever (F) - The ffort () and esistance () are located on the same side of fulcrum, but the ffort () acts between fulcrum and the esistance () as shown in Figure 3 Third Class Lever. xamples of a third class lever include a shovel and a broom. A large effort gains speed of motion in this type of lever. It is the most common lever type in the human 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 ffort Contest 2004 The University of Texas Health Science Center at San Antonio 3 Activity Overview Continued

4 Activity Management Suggestions: Students should work in groups of two to four. emind students to use good time management skills and to divide the jobs equally so every member of the group has a fair share of the tasks. During the processing out time, be sure that students have discovered the unexpected result related to third class levers. Students expect to find that each lever will reduce the amount of force needed to move an object and will be surprised to find that the third class lever actually has a mechanical disadvantage. This concept will be important for students as they progress to the next activity on biomechanics of levers in the human body. xtension: Students can collect household tools and determine which type of lever they represent. Activity eferences Used: Broer, M. (1973) fficiency of human movement (Third dition). Philadelphia: W.B. Saunders Company. Gowitzke, BA & Milner, M. (1988). Scientific bases of human movement (Third dition). Baltimore: Williams & Wilkins. Gray, H. (1918). Anatomy of the human body (20th dition). Philadelphia: Lea & Febiger. Hamill, J. & Knutzen, KM. (2003). Biomechanical basis of human movement (Second dition). New York: Lippincott Williams & Wilkins. Activity Overview Continued 2004 The University of Texas Health Science Center at San Antonio 4

5 Activity Administrivia : Key Concepts: Classes of levers, Forces at work in each class of lever Process Skills utilized in Activity: Observing, Inferring, Measuring Previous learning assumed: Concept of Force, Use of spring scale, Group skills, following directions Intended Grade Level: 6-8 elevant TKS: 6.1 A The student conducts field and laboratory investigations using safe, environmentally appropriate, and ethical practices. The student is expected to demonstrate safe practices during field and laboratory investigations 6.2 The student uses scientific inquiry methods during field and laboratory investigations. The student is expected to: (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 () construct graphs, tables, maps, and charts using tools including computers to organize, examine, and evaluate data. 6.4 The student knows how to use a variety of tools and methods to conduct science inquiry. The student is expected to: (A) collect, analyze, and record information using tools including beakers, petri dishes, meter sticks, graduated cylinders, weather instruments, timing devices, hot plates, test tubes, safety goggles, spring scales, magnets, balances, microscopes, telescopes, thermometers, calculators, field equipment, compasses, computers, and computer probes; 7.1 Scientific processes. The student conducts field and laboratory investigations using safe, environmentally appropriate, and ethical practices. The student is expected to: (A) demonstrate safe practices during field and laboratory investigations 7.2 Scientific processes. The student uses scientific inquiry methods during field and laboratory investigations. The student is expected to: (B) collect data by observing and measuring; (C) organize, analyze, make inferences, and predict trends from direct and indirect evidence; (D) communicate valid conclusions; and () construct graphs, tables, maps, and charts using tools including computers to organize, examine, and evaluate data. 7.4 Scientific processes. The student knows how to use tools and methods to conduct science inquiry. The student is expected to: (A) collect, analyze, and record information to explain a phenomenon using tools including beakers, petri dishes, meter sticks, graduated cylinders, weather instruments, hot plates, dissecting equipment, test tubes, safety goggles, spring scales, balances, microscopes, telescopes, thermometers, calculators, field equipment, computers, computer probes, timing devices, magnets, and compasses 7.6 The student knows that there is a relationship between force and motion. The student is expected to: (A) demonstrate basic relationships between force and motion using simple machines including pulleys and levers 8.1 The student conducts field and laboratory investigations using safe, environmentally appropriate, and ethical practices. The student is expected to: (A) demonstrate safe practices during field and laboratory investigations 8.2 The student uses scientific inquiry methods during field and 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 () construct graphs, tables, maps, and charts using tools including computers to organize, examine, and evaluate data. 8.4 The student knows how to use a variety of tools and methods to conduct science inquiry. The student is expected to: (A) collect, record, and analyze information using tools including beakers, petri dishes, meter sticks, graduated cylinders, 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 2004 The University of Texas Health Science Center at San Antonio 5

6 Little Bit of ffort SISTANC FFOT SISTANC FFOT SISTANC FFOT presented to for exemplary knowledge of levers. TACH DAT 2004 POTOTYP 2004 The University of Texas Health Science Center at San Antonio 6

7 Just a Little Bit of ffort: xploring Levers Student Activity Page Activity Introduction: How many times have you used a broom, rake, pair of pliers, wheelbarrow, pry bar or played on a see saw? ach of these items involves a simple machine; the lever. Simple machines are designed to make work easier in some way, so they are good to 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 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, and effort relative to each other. The combination of these relative locations results in first class, second class and third class levers. First class lever (F)- The ffort () and esistance () are located on opposite sides of fulcrum as shown in Figure 1: First Class Lever below. xamples of a first class lever include pry bars, see saws, crowbars. Figure 1 First Class Lever 2004 The University of Texas Health Science Center at San Antonio 7

8 Second Class lever (F) - The ffort () and the esistance () are located on the same side of fulcrum and the esistance () is between fulcrum and ffort () 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 (F) - The ffort () and esistance () are located on the same side of fulcrum, but the ffort () acts between fulcrum and the esistance () as shown in Figure 3 Third Class Lever shown below. xamples 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 in the human body. Figure 3 Third Class Lever 2004 The University of Texas Health Science Center at San Antonio 8

9 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: (ead 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 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. 2cm Spring Scale Stand Hook 28cm Pull up to measure force required to balance Binder Clip 1 N weight Figure 1 Constructing a First Class Lever b. Pull on the spring scale until the wooden ruler is level; the lever now is balanced and is in equilibrium. c. ead the force you are applying (ffort) in Newtons on the spring scale and record it in Table 1, xploring First Class Levers on your Student Data Page. d. epeat steps a c placing the hanging weight (esistance) at 4 cm and the spring scale to measure the ffort in Newtons at 28 cm. e. epeat steps a c, using the locations for the ffort and esistance provided in Table 1, xploring First Class Levers. ecord your measurements in Table 1, xploring First Class Levers on your Student Data Page The University of Texas Health Science Center at San Antonio 9

10 3. Second Class Levers a. Create a second class lever on the wooden stand. Place the fulcrum at 2 cm, the hanging weight (esistance) at 6 cm and the spring scale to measure the ffort 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. ecord this information in Table 2 xploring in a Second Class Levers. b. epeat step a using the locations for the esistance and ffort and recording the data in Table 2 xploring Second Class Levers. 4. Third Class Levers a. Create a third class lever on the wooden stand. Place the fulcrum at 2 cm, the hanging weight (esistance) at 6 cm and the spring scale to measure the ffort 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. ead the amount of force you are exerting to keep the lever in equilibrium and record all data in Table 3 xploring Third Class Levers. b. epeat step a using the other locations for the esistance and ffort and recording the data in Table 3 xploring Third Class Levers. 5. The Great Little Bit of ffort Contest 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 ffort Contest. 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. 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. d. epeat steps b c for your second class lever design. e. epeat steps b c for your third class lever design. f. When you finish with all three parts of the contest, you will complete Table 4, The Little Bit of ffort Contest, including calculating the ratio of esistance Force ffort Force for each class of levers you design. The ratio you calculate is called the mechanical advantage of your lever system. g. When you finish Table 4, fill out the Little Bit of ffort Contest ntry Form and wait for the results! 2004 The University of Texas Health Science Center at San Antonio 10

11 Just a Little Bit of ffort: xploring Levers Student Activity Data Sheet I. xploring First Class Levers Table 1 xploring First Class Levers Location of ffort (cm) Distance Between Fulcrum and ffort (cm) ffort Force (N) Location of esistance (cm) Distance Between esistance and Fulcrum (cm) esistance Force (N) 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 resistance were 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? 2004 The University of Texas Health Science Center at San Antonio 11

12 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 counterbalance 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 xploring First Class Levers. When the esistance was further from the fulcrum than the ffort, what happened to the amount of ffort required to balance the resistance? 7. What is the effect of distance from the fulcrum on this lever system? (Be sure to discuss both esistance (load) and ffort.) II. xploring Second Class Levers (Put the fulcrum at 2cm) Table 2 xploring Second Class Levers Location of ffort (cm) Distance Between Fulcrum and ffort (cm) ffort Force (N) Location of esistance (cm) Distance Between esistance and Fulcrum (cm) esistance Force (N) The University of Texas Health Science Center at San Antonio

13 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 make this lever more efficient? Why or why not? 6. Look at your data in Table 2 xploring Second Class Levers. When the esistance was further from the fulcrum and the location of the effort stayed the same, what happened to the amount of ffort required to counterbalance the resistance? 7. What is the effect of distance from the fulcrum on this lever system? Be sure to discuss both esistance (load) and ffort) The University of Texas Health Science Center at San Antonio 13

14 III. xploring Third Class Levers (Put the fulcrum at 2cm) Table 3 xploring Third Class Levers Location of ffort (cm) Distance Between Fulcrum and ffort (cm) ffort Force (N) Location of esistance (cm) Distance Between esistance and Fulcrum (cm) esistance Force (N) 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? 2004 The University of Texas Health Science Center at San Antonio 14

15 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 make this lever more efficient? Why or why not? 6. Look at your data in Table 3 xploring Third Class Levers. When the esistance was further from the fulcrum and the location of the effort stayed the same, what happened to the amount of ffort required to counterbalance the resistance? 7. What is the effect of distance from the fulcrum on this lever system? (Be sure to discuss both esistance (Load) and ffort). 8. What unexpected results did you find when you worked with the third class lever? 2004 The University of Texas Health Science Center at San Antonio 15

16 IV. The Little Bit of ffort Contest Contest Table 4 Little Bit of ffort Contest (atio of esistance/ffort) Name(s) Little Bit of ffort Contest ntry Form FIST CLASS SISTANC FFOT SCOND CLASS SISTANC FFOT SISTANC THID CLASS FFOT / 2004 The University of Texas Health Science Center at San Antonio 16