What can you use a lever for?
Why were levers invented?
Why is it a good idea for people to know how to use a lever?
What is force?
How do scientists learn about different things?
More than one force acts on an object along a straight line; the forces will
reinforce or cancel one another, depending on the direction and magnitude.
Unbalanced forces change the speed or direction of an objects motion.
A lever is a simple machine that people use to gain an advantage, such as making work easier.
An advantage is a benefit obtained by using a lever.
Effort is the force needed to move a load or overcome a resistance.
A fulcrum is the point where a lever arm pivots.
Load is a mass lifted or a resistance overcome by a lever.
Scientists identify questions, create and conduct experiments to answer those
Scientists use data to construct reasonable explanations
Use mathematics in the scientific process
Use various tools to gather, analyze, and interpret data
Individuals work together in teams and use tools and scientific techniques
to make observations
Many different people have made contributions to science and technology.
Science relies on basic human qualities such as reasoning, insight, energy, skill and creativity as well as on scientific habits of mind, such as intellectual honesty, tolerance of ambiguity, skepticism, and openness to new ideas.
Levers give their users some form of advantage when working. It is the most common simple machine. They can be found in almost every room in a house and are incorporated into the construction of cars, refrigerators, toys, televisions, sports equipment, and the human body. Teeter-totters, crowbars, can openers, brooms and arms are all examples of levers. A lever is a beam, called a lever arm, that is free to rotate around a fixed point, called a fulcrum. If a lever pivots on a fulcrum that is in the middle of the lever arm, a push down (force) on one end will make the other end go up. Force is measured in newtons. A mass of 1 kg. pulls or pushes down (because of gravity) with a force of 10N. There are three classes of levers class 1 levers, class 2 levers and class 3 levers.
Foss Science Kit: Simple Machines
Lever and advantage
2 spring scales with rubber bands, 2 loads (cubes) with rubber bands, 2 half-meter sticks, 2 Binder clips, 2 Dowels, 2 Erasers, pencil-cap, science journal
1. Ask students how they would open a can of paint, such as house paint. What would they use to open it? How would they use the tools they suggested to get the can of paint open?
2. Allow all students to respond. Do not give any indications as to a right or wrong answer.
3. Explain to students that the tools a person would use to open the can of paint are called levers. They give the person an advantage to opening the can.
4. Introduce the lever journal and explain to students they are starting a series of scientific investigations with lever systems. They will need to keep good records of their observations.
5. Set up the first lever system. Allow students to watch. Tape a dowel to the desk with two pieces of duct tape(one close to the edge of the desk and one at the very end of the dowel) so the dowel hangs over the desk about 5 cm. Next take the half meter stick and attach a binder clip in the middle (this will be the zero position) Flip the metal loops of the binder clip up. This will be the lever arm. Slip the loops over the dowel so that it will rotate. Adjust the location of the clip on the half-meter stick until it balances. Slide a wedge-shaped eraser on the end of the dowel. Hold up one of the cubes. Point out the rubber band attached to the hook. The mass lifted by the lever is the load. Hang the load, using the rubber band, on one side of the half-meter stick. Hang the spring scale, using the rubber band, on the other side of the half-meter stick. (The teacher will need to review with the students how to correctly read a spring scale.) The effort is the force (push or pull) needed to lift or move the load. Explain that when the load hangs on the lever or on the spring scale, it pulls down with force. Show students how you can move the load up and down using one finger on the opposite side of the lever.
6. Put students into pairs to set up their own lever systems. Allow them to begin free exploration.
7. After the students have their lever systems set up and explored for about five minutes, bring them back together.
8. Ask the groups to set up a lever system with the load hanging at 15 cm and 30 cm. Present these questions: Can you lift the load using one finger? Does it always take the same amount of force to lift the load? Where should you press to lift the load with the least force?
9. Allow students to explore again for several minutes and explore the questions presented.
10. Bring students back together to discuss the advantage of using levers to lift heavy objects.
11. Ask how they used data to understand a lever system.
12. What tools did they use to gather data? How did they measure? How did they learn?
13. How did what they did compare to what scientists do?
14. How can they use what they learned today?
15. Ask students to record their findings for the day and write a short paragraph about how levers provide individuals with an advantage.
"Lift the Load"
2 spring scales with rubber bands, 2 loads (cubes) with rubber bands, 2 half-meter sticks, 2 Binder clips, 2 Dowels, 2 Erasers, pencil-cap, science journal, experiment sheet
1. Ask what they learned about the lever in activity one.
2. Ask where levers are used in the world.
3. Ask what happened as they moved the load.
4. Ask how much force (effort) is needed to lift a load of cubes?
5. Have students set up lever systems (same as previous experiment) and explore how much effort is needed to lift the given load. Observe to see if any group or individual discovers they can read the force needed to lift the load.
6. Explain that when the load hangs on the lever or on the spring scale, it pulls down with force.
7. Bring the students back together as a class and have them discuss what procedure they can use to lift the load of cubes. Make sure the students explain the following or ask questions and/or explain that: The scale can be used for measuring the amount of force needed to lift a load. Create an experiment sheet for each student to record the data. The data sheet could have the same amount of mass for the load (controlled variable) in the same location (controlled variable) and different distances for the effort (manipulated variable). Example the load stays at 10 cm, and the effort is applied at various distances from the fulcrum (5-cm intervals except for the first one at 2.5 cm.)
8. Make sure they have a way to record the effort needed to lift the load for each position. A chart or graph with distance from fulcrum and effort to lift as label. A graph would have the distance on the x axis and mass or force to lift it on the y axis.
9. If students desire the teacher may present a demonstration to the students. Put the load 5-cm from the fulcrum. Put the scale 25-cm from the fulcrum on the other side. Tell the students, the load is 5 cm from the fulcrum. How much pull is being applied to lift the load? Ask a student to read the scale. He/she will report 0.0 N. Ask the students, How is the load being lifted with no effort? How is that possible? If the weight of the scale is lifting the load, how can we find out how many newtons that is?
10. Suggest that the students use one scale to weigh another. They will discover that the weight of the scale exerts a force of .05 N.
11. Now ask the students to calculate the total force. If needed you can probe If the scale itself pulls with a force of 0.5 N, what is the total pull applied to the lever system in each measurement in the experiment you just completed.
12. Explain to the students that the scale reading does not include the 0.5 N pull of the scale itself. The total effort is the sum of the reading on the scale plus the 0,5 pull of the scale. Students should record this sum in the right side of the "effort" column.
13. Now students are ready to begin their own investigation with the experiment sheet provided. Allow students plenty of time to record their data.
14. Ask how they can use the data and or graph to understand a lever system.
15. What tools did they use to gather data? How did they measure? How did they learn?
16. How did what they did compare to what scientists do?
17. How can they use what they learned today?
18. Then ask each student to respond to these three questions in their science journal. Does the lever provide an individual with an advantage? Did the amount of force needed to lift the load change when you moved the position of the effort? What is the relationship between the position of the effort and the amount of effort needed to lift the load?
Modifications to "Lift the Load"
2 Spring scales with rubber bands, 2 Loads (cubes) with rubber bands, 2 Half-meter sticks, 2 Binder clips, 2 dowels, 2 Erasers, pencil-cap, Levers Journal, Experiment Sheet
1. Ask the students what they learned about the lever and the advantage it provides to lifting a heavy load.
2. What do you think would happen to the effort needed to lift the load if the scale stayed at one location on the lever or if the load moved farther and farther from the fulcrum?
3. Would you get the same results you did with yesterdays experiment?
4. Explain to the students that they are going to explore today using these questions.
5. Demonstrate how to set up the experiment. (The scales will be set up in the same manner as they were for the two previous experiments. Teachers will point out that the scale will stay at 10 cm and the load will move from place to place.)
6. Have the students get into groups and discuss what may happen. Have each student record their predictions in their journal.
7. With students in groups of twos, have them begin the experiment. The process will be the same as the previous lesson only they will move the load to various locations on their ruler.
8. Tell students to record their findings on the experiment sheet provided.
9. Observe the students as they work and make sure each group is completing the experiment in the correct way. Help students or groups who may become confused throughout the process especially measuring correctly after moving the load.
10. How do your results of yesterdays experiment compare with those of today?
11. How did you measure? How did you collect your data? What did you use to gather your data?
12. What is the relationship between the location of the load on the lever system and the effort it takes to move it?
13. Why is the location of the load an important factor in the lifting process?
14. Conclude with a discussion about the results. Ask the students to compare their results from today with those of yesterdays experiment. Ask the students to respond to these questions in their journal.
2 Half-meter sticks, 2 Binder clips, 2 Dowels, 2 Erasers, pencil cap, 2 Spring scales with rubber bands,
2 Loads with rubber band, 3 Lever Diagram posters, Duct Tape, Masking Tape
1. Set up the demonstration lever system. Ask the students to review with you the components of the lever system. (Lever arm, fulcrum, load and effort)
2. Ask the students what they remember about levers providing an advantage for the user.
3. What advantages do levers provide?
4. How do scientists use levers in their work?
5. Hang a load on your lever.
6. What is a force? (push or a pull)
7. Explain that when the load hangs on the lever or on the spring scale, it pulls down with force.
8. Now place the load at 20 cm. Place the spring scale at 10 cm on the other side of the lever.
9. Will the effort needed to lift the load be more, less, or the same as the pull of the load?
10. After the students make their predictions, lift the load and have a student come read the effort. (The effort required (scale reading plus 0.5N) will be about 4.8N, which is twice the force of the load pulling down.)
11. The lever has the fulcrum in the middle of the lever arm. Is the fulcrum always right in the middle of the lever arm?
12. What might happen if the lever was not in the middle? Would it still be a lever?
13. Is there any advantage to moving the fulcrum to new locations along the lever arm?
14. Now allow the students to set up their own lever systems and explore what happens when they move the placement of the fulcrum.
15. As students explore the possibilities, move around the room and ask different groups what they are finding out about the placement of the fulcrum. (Students should report that the closer the fulcrum gets to the load, the easier the load is to lift.)
16. Tell the students they have been working with class-1 lever systems. Class-1 levers always have the fulcrum somewhere between the load and the effort.
17. Now ask students if they can think of other arrangements of load, effort, and fulcrum?
18. Draw their suggestions on the board, making sure that one has the load in the middle an done has the effort in the middle.
19. Tell students to return to their groups and explore new ways to set up a different kind of lever system. Try to find out what kind of advantage (if any) it provides. Allow students time to solve the problems they find with these new lever systems. It may take some time for them to realize that the effort must be applied in an upward direction sometimes. Be patient and let them explore it.
20. If after some time the students are not having success, bring them back as a whole group and provide them with a couple of helpful hints. Demonstrate how to place the binder clip on the end of the lever arm. It should be placed under the zero end of the metric side of the half-meter stick. Tell students to use this side of the lever arm. You may also need to suggest that some levers might work with the effort going upward, rather than downward as they did in previous explorations.
21. Allow the students to return to work in their small groups and after all groups have worked with at least one new lever system, introduce the new lever vocabulary. Levers with the fulcrum in the middle are class-1 levers, levers with the load in the middle are class-2 levers and levers with the effort in the middle are class-3 levers.
22. In the time remaining with the rest of class, have students set up an example of each of the three classes of levers. They should notice which ones seem to provide the greatest advantage to the user.
23. For closing, bring all students back together and discuss with all of them the three types of lever systems.
24. What is important about the placement of the fulcrum?
25. Does it always have to be placed in the same place?
26. Does the placement affect the amount of effort needed to lift a load?
27. Allow for a few minutes at the end so that students may journal in their notebooks about the lever classes they discovered in todays lesson.
Real World Levers
1 Broom, 1 Nutcracker, 1 Scissors, 1 Bottle Opener, 1 Pliers, 1 Tweezers, 1 Hammer, Half-meter sticks, Loads with rubber band, Masking tape, Lever Diagram Poster (optional), Lever Picture Poster (optional)
1. Where can you find levers?
2. What are some daily household jobs in which levers are used?
3. What types of machines use levers?
4. Can you think of any sports or other activities that use levers?
5. Tell students that levers are all around them. They are in every toolbox and kitchen-utensil drawer. They are found in toys, appliances, cars, and construction machinery.
6. Review the classes of levers with the students. Ask them to explain each lever class and the way it is different from the other two. The class-1 lever has the fulcrum in the middle, with the load on one side and the effort on the other. A crowbar is an example of a class-1 lever.
7. Continue the discussion with students about class-2 and class-3 levers. An example of a class-2 lever is a wheelbarrow while a class-3 lever is a broom.
8. Explain to the students they have a number of tools to explore and investigate. Each tool uses one or more levers to give its user some kind of advantage. Tell them to investigate the tool, analyze it to find the lever, draw a diagram of the tool identifying where the load, fulcrum and effort are located and write the class of levers it belongs to.
9. Do one example together so the students understand what they are going to do. Use a screwdriver to open a can of paint.
10. What class of lever is the screwdriver when it is used to pry the lid off a can? When you are trying to lift the lid off a can of paint, there is no metal cube to be lifted.
11. Where is the load, and what direction is the load acting?
12. Explain to the students that load can be either a mass that you can lift or a resistance that you need to overcome. The tight lid on the can requires a lever to get it loose. The resistance is the load. You try to lift the lid up, so the resistance (load) is acting down.
13. Have the students identify the load, fulcrum, effort and class of the screwdriver and paint can.
14. Divide the students into eight groups. Assign each group a number. The number will correspond to the numbered object they will investigate first. Put the numbered objects at the materials station.
15. Have each group pick up the appropriate tool and begin investigating it.
16. The teacher may need to help some groups get started by helping them identify the resistance (the nut in the nutcracker) as the load in the system. The nut resists being crushed, so it is pushing out against the jaws of the nutcracker. Once each group is going and working with their tool, the teacher should continue to observe and help with any problems a group may have.
17. The students will need to diagram each tool they investigate in their levers journal. When they have finished diagramming one tool, have the groups switch tools so they can investigate another tool.
18. Continue this procedure until all groups have explored each tool and diagrammed it in their levers journal.
19. What did you find out about each tool?
20. Were they all levers?
21. Do scientists ever use any of these tools?
22. How do these tools make our daily lives easier?
23. Encourage the students to think of other things around the classroom or home that are levers. Make a list on the board and have them record that in their science journals.
A seesaw, wheelbarrow, buckets of dirt or sand, science journal
1. What are some of the levers we have discussed in the last few days?
2. How can the levers be used? How do levers make our lives easier?
3. How does the placement in parts on a lever make it different?
4. Begin by reviewing what a lever is and the different parts and classes of levers.
5. Take the students out to the playground area and have the students try and lift the teacher on the seesaw, to see how many students it takes to do so. Continue doing this exercise by moving the fulcrum. How far off the ground is the teacher?
6. All levers have three parts. What was involved in using this lever? (The fixed part (fulcrum), the teacher (load) and the push of the other students (effort)). Have the students chart the data on how many students it took and the position of the fulcrum.
7. Have the students walk around the playground and see if they can find other levers. What class, and the different parts where they are located.
8. Next have the children try and carry one bucket full or sand or dirt from one point to another. Making sure the bucket is heavy. Have wheelbarrows close by and ask the students what they think might make it easier to move the dirt. When they say use of the wheelbarrows have them use them to move the buckets the same distance.
9. Have them describe the parts of the wheelbarrow and compare with a lever. Ask them which way was easier to move and why.
10. Take students back in and discuss the two types of levers used and name the parts.
11. Can you think of other equipment on the playground that can be consider a lever?
12. What other types of garden tools can you think of? How are those tools used?
13. Maybe ask about other types of garden tools that make-work easier, make a list and have them record in their journals.
14. Have the students use their journals, making diagrams and documenting the activity.
Three Classes of Levers Presentation
Note: This activity is a cumulative activity for the unit. The students will be asked to create a presentation on a class of levers.
1. Begin by having the students give an example of the three classes of levers. Have a student come to the board and put up a simple drawing of the lever and label the parts and class.
2. Once the class has discussed the levers and classes, divide your class into three groups. The students will then draw from the three classes to see which class they will do a report on.
3. The groups will begin by drawing pictures of levers in that class and writing explanations as to how it works. The students will be asked to create a PowerPoint that is no longer than 10 frames and no shorter than 8. In the presentation they will be asked to talk about how their class of levers works, the different parts of the lever, and at least 4 examples. Each student will be responsible for at least one frame.
4. Over the next class periods the students will create, edit, and present their final product. The teacher will oversee and help in any trouble spots the groups may have.
5. The students will each present their part of the presentation, telling what it is from their frame they learned. The teacher will assess the students knowledge of the class of lever they were assigned.
6. The activity can be drawn to closure by talking briefly about each class of levers and the uses.