Lever - Rokenbok Education | See Like A Designer, Think ... Build & Modify Test and Modify the Third...
Transcript of Lever - Rokenbok Education | See Like A Designer, Think ... Build & Modify Test and Modify the Third...
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Progression: Applications in Design & Engineering - Section 2 Curriculum Packet
Lever
IntroductionThis Rokenbok STEM-Maker lesson will use the following steps to learn about the lever.
Key Terms
Simple Machine: A device that transmits or modifies force or motion.
Lever: A simple machine consisting of a rigid beam that pivots on a fulcrum. It is used to redirect motion, increase output speed, or create mechanical advantage.
Fulcrum: The point or support on which a lever pivots.
Leverage: The mechanical advantage gained by using a lever.
Mechanical Advantage: The amount a machine multiplies force.
Force: A push or a pull.
Work: Using a force to move an object a distance.
Effort: A force applied to a machine to do work.
Load: The object or weight being moved or lifted.
Learning Objectives
Understand the basic elements and purpose of a lever.
Understand the difference between a class 1, 2, and 3 lever.
Calculate the amount of mechanical advantage in a lever.
Modify a lever to increase mechanical advantage.
Design and engineer a custom leverto solve a challenge.
Elements of a lever Purpose of a lever Different types of levers Mechanical advantage in a lever
1. Learn 2. Build & Modify
3. Design & Engineer
Build a lever Test a lever Modify a lever to increase mechanical advantage
Design and engineer a custom lever to solve a challenge
Resources
SnapStack Module
*4 Students Per Module
Programmable Robotics Module
*4 Students Per Module
Advanced Projects Lab
*4 Students Per Lab
or or
v2.0
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Building Basics
Rokenbok Building BasicsThe following tips will be helpful when using the Rokenbok Student Design & Engineering System.
Connecting/Separating ROK Blocks:
ROK Blocks use a friction-fit, pyramid and opening system to connect. Simply press pyramids into openings to connect. To separate blocks, pull apart.
Connecting/Separating Rokenbok Components:
Smaller Rokenbok components use a tab and opening system to connect. Angle one tab into the opening, and then snap into place. To separate, insert key into the engineered slot and twist.
Snapping Across Openings:
The tabs on Rokenbok components can also be snapped across openings to provide structural support to a design. This will also allow certain designs to function correctly.
Attaching String:
In some instances, string may be needed in a design. Lay string across the opening and snap any Rokenbok component with tabs or pyramids into that opening. Be sure that the tabs are perpendicular to the string to create a tight fit.
2cm18cm
9 Openings
6cm
3 OpeningsMeasuring:
The outside dimensions of each Rokenbok connector block are 2 cm3. This means the length, depth, and height are each 2 cm. To determine the size of a Rokenbok build in centimeters, simply count the number of openings and multiply by two. Repeat this process for length, depth and height.
2cm
2cm
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The LeverA lever is a simple machine that consists of a rigid beam (lever arm) that pivots on a fulcrum. It is used to redirect motion, create mechanical advantage to make work easier, or increase output speed to make a load move faster.
Types of LeversThere are three types of levers, according to where the load and effort are located in respect to the fulcrum.
First Class LeverIn a first class lever, the fulcrum is located between the effort and the load. A first class lever can be used to reduce the amount of effort needed to raise a load by placing the fulcrum closer to the load, or to increase output speed by placing the fulcrum closer to the effort.
Second Class LeverIn a second class lever, the load is located between the effort and the fulcrum. The amount of effort needed to raise a load is reduced as the load is placed closer to the fulcrum. A second class lever does not change the direction of motion because the effort and the load move in the same direction.
Third Class LeverIn a third class lever, the effort is applied between the load and the fulcrum. The amount of effort needed to raise the load is reduced as the effort is applied closer to the load. A third class lever is primarily used to increase output speed, which increases as the effort is applied closer to the fulcrum.
Learn
First Class Lever
Second Class Lever
Example BThird Class Lever
Real World ApplicationsThe lever is used in many different ways to make work easier. Here are some real world examples.
Scissors Catapult Wheelbarrow Foot Pump Baseball Bat Hammer
Rigid Beam (Lever Arm)
Fulcrum
Effort
Load
FulcrumLever Arm
Effort
Load
FulcrumLever Arm
Effort
Load
Fulcrum
Lever Arm
First Class Second Class Third Class
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Build & Modify
InstructionsFollow the step-by-step instructions to build a first class lever.
1 2
3
3x Beam
1x Single Snap Block
4x Block
2x Half Beam
1x Hinge Block
2x Block
2x Snap-In Wheel
1x Beam
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Build & Modify
Test and Modify the First Class LeverFollow the instructions to test and modify the first class lever.
The fulcrum in this example has been centered between Weight 1 (Effort) and Weight 2 (Load). Lift Weight 1 (Effort) as high as possible and let go. Observe how nothing happens. This is because the two weights balance each other equally.
Testing the First Class Lever
Modifying the First Class Lever
First Class Lever
EffortLoad
FulcrumLever Arm
Weight 1EffortWeight 2
Load
First Class Lever
Effort
Load
FulcrumLever Arm
In a first class lever, the amount of effort needed to raise a load is reduced as the fulcrum is moved closer to the load. Move the fulcrum 1.5 openings towards Weight 2 (Load) as shown in the figure to the right. Now, lift Weight 1 (Effort) as high as possible and let go. Observe how Weight 1 (Effort) drops to the base, and Weight 2 (Load) is raised to its highest position. In this example, the fulcrum is closer to the load than it is to the effort. This modification allows Weight 1 (Effort) to travel a further distance and raise Weight 2 (Load). Observe how far wheel 1 (Effort) travels in relation to wheel 2 (Load).
Weight 1EffortWeight 2
Load
Fulcrum
Fulcrum
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Build & Modify
InstructionsFollow the step-by-step instructions to build a second class lever.
1 2
3
3x Beam
1x Single Snap Block
4x Block
2x Half Beam
1x Hinge Block
2x Block
2x Snap-In Wheel
1x Beam
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Test and Modify the Second Class LeverFollow the instructions to test and modify the second class lever.
In a second class lever, the load is placed between the fulcrum and the effort. In this example, when Wheel 1 (Effort) is raised, Wheel 2 (Load) is raised in the same direction.
Testing the Second Class Lever
Modifying the Second Class Lever
Second Class Lever
Wheel 1Effort
Wheel 2Load
Second Class Lever
In a second class lever, the amount of effort needed to raise a load is reduced as the load is moved closer to the fulcrum. Move Wheel 2 (Load) 3 openings towards the fulcrum as shown in the figure to the right. Lift Wheel 1 (Effort) to raise Wheel 2 (Load). There should be a noticeable difference in the amount of effort needed to raise the load. As the load is moved closer to the fulcrum, the effort will travel a further distance to raise the load. Observe how far Wheel 1 (Effort) travels in relation to Wheel 2 (Load).
Effort
Load
FulcrumLever Arm
Wheel 1Effort
Wheel 2Load
Build & Modify
EffortLoad
FulcrumLever Arm
Fulcrum
Fulcrum
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Build & Modify
InstructionsFollow the step-by-step instructions to build a third class lever.
1 2
3
3x Beam
1x Single Snap Block
4x Block
2x Half Beam
1x Hinge Block
2x Block
2x Snap-In Wheel
1x Beam
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Build & Modify
Test and Modify the Third Class LeverFollow the instructions to test and modify the third class lever.
In a third class lever, the effort is applied between the fulcrum and the load. In this example, when Wheel 1 (Effort) is raised, Wheel 2 (Load) is raised in the same direction. The amount of effort needed to raise a load is reduced as the effort is applied closer to the load.
Testing the Third Class Lever
Modifying the Third Class Lever
Third Class Lever
Wheel 1Effort
Wheel 2Load
Third Class Lever
The primary purpose of a third class lever is to increase output speed. Move Wheel 1 (Effort) 4 spaces towards the fulcrum as shown in the image to the right. In this example, when Wheel 1 (Effort) is raised, Wheel 2 (Load) is raised in the same direction. As the effort is applied closer to the fulcrum, the load will travel a further distance than the effort in the same amount of time. Observe how far Wheel 2 (Load) travels in relation to Wheel 1 (Effort).
Wheel 1Effort
Wheel 2Load
Effort
Load
Fulcrum
Lever Arm
Effort
Load
Fulcrum
Lever Arm
Fulcrum
Fulcrum
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Understanding Mechanical AdvantageThe main purpose of a simple machine is to make work easier. This is done by redirecting motion, increasing speed, or creating mechanical advantage. Mechanical Advantage exists when the output force of a machine is greater than the input force that was applied to it. To accomplish this, the machine must trade increased time or distance for reduced effort. The mechanical advantage gained by using a lever is called leverage.
First Class Lever
A first class lever can be used create mechanical advantage by placing the fulcrum closer to the load. To calculate how much mechanical advantage is in a first class lever, divide the Input distance (distance from the effort to the fulcrum) by the Output distance (distance from the load to the fulcrum).
In the modified first class lever, the input distance was 6 blocks (12 cm), and the output distance was 3 blocks (6 cm). Divide 12/6 and this will give a mechanical advantage of 2:1. This lever is able to output two times the amount of force that is applied to it. Wheel 1 (Effort) will travel twice the distance of Wheel 2 (Load) in order to reduce the amount of effort needed to raise the load.
Second Class Lever
A second class lever can be used create mechanical advantage by placing the load closer to the fulcrum. To calculate how much mechanical advantage is in a second class lever, divide the Input distance (distance from the effort to the load) by the Output distance (distance from the load to the fulcrum).
In the second class lever that was built and modified, the input distance was 6 blocks (12 cm), and the output distance was 2 blocks (4 cm). Divide 12/4 and this will give a mechanical advantage of 3:1.This lever is able to output three times the amount of force that is applied to it. Wheel 1 (Effort) will travel three times the distance of Wheel 2 (Load) in order to reduce the amount of effort needed to raise the load.
Third Class Lever
To calculate how much mechanical advantage is in a third class lever, divide the Input distance (distance from the effort to the fulcrum) by the Output distance (distance from the load to the fulcrum).
In the third class lever that was built and modified, the input distance was 2 blocks (4 cm), and the output distance was 8 blocks (16 cm). Divide 4/16 and this will give a mechanical advantage of .25:1. This means that Wheel 2 (Load) will travel four units of measurement for every one unit of measurement Wheel 1 (Effort) travels in the same amount of time. The mechanical advantage of a third class lever will always be less than 1, which means it is not actually creating any mechanical advantage. Its primary purpose is to increase output speed. Output speed is increased as the effort is applied closer to the fulcrum.
Build & Modify
Input distance (effort to fulcrum)Output distance (load to fulcrum)
MechanicalAdvantage =
First Class Lever
Fulcrum
Output Distance3 Blocks (6 cm)
Input Distance6 Blocks (12 cm)
Weight 2Load
Weight 1Effort
Input distance (effort to load)Output distance (load to fulcrum)
MechanicalAdvantage =
Second Class Lever
Input distance (effort to fulcrum)Output distance (load to fulcrum)
MechanicalAdvantage =
Third Class Lever
Output Distance2 Blocks (4 cm)
Input Distance6 Blocks (12 cm)
Weight 1 Effort
Weight 2 Load
Fulcrum
Output Distance8 Blocks (16 cm)
Fulcrum
Weight 2Load
Input Distance2 Blocks (4 cm)
Weight 1 Effort
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Design & Engineering Challenge: Catapult
In this challenge, each team must design and engineer a custom catapult. Read carefully through the design brief below, then use the design and engineering process to develop a solution to the challenge.
Design & Engineer
Design Brief: Scenario
A local museum is looking to add a medieval times themed area to a newly renevoted part of their building. They would like to include an interactive display that can be used by children to test a small, working, medieval catapult system. Children will have fun testing the catapult for distance and precision, while also learning how the devices were used in medieval times.
Design & Engineering Challenge
Your challenge is to design and engineer a catapult device that can precisely launch Rokenbok balls to hit close and long range targets.
*Instructor will have close and long range targets set up for testing catapults.
Specifications & Sub-Challenges
1. Teams can work in groups of up to four to complete this challenge.
2. Teams must work through each step of the design and engineering process to design, prototype, and refine a custom catapult. Teams will be responsible for written documentation in the student engineering workbook.
3. Sub-Challenge: The catapult must feature a lever that creates mechanical advantage.
4. Sub-Challenge: The catapult must feature a safety locking pin that can be used to prevent accidental launching.
5. Sub-Challenge: The catapult must include a gauge that can be used to precisely launch balls to close and long range distances.
6. Sub-Challenge: With each building component costing $2, the catapult must cost less than $140.
7. The catapult must be structurally strong and aesthetically appealing.
8. Each team will be required to effectively explain all aspects of brainstorming, prototyping, testing and improving the design.
Design & Engineering Process
To develop a high quality design, teams will work through each step of the design & engineering process. Teams should track all progress in the student engineeringworkbook.
Design and Engineering Process Student Engineering Workbook
Input Distance6 Blocks (12 cm)
Output Distance8 Blocks (16 cm)
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Design & Engineer
Challenge EvaluationWhen teams have completed the design & engineering challenge, it should be presented to the teacher and classmates for evaluation. Teams will be graded on the following criteria:
Specifications: Does the design meet all specifications as stated in the design brief?
Performance: How well does the design work? Does it function consistently?
Team Collaboration: How well did the team work together? Can each student descibe how they contributed?
Design Quality/Aesthetics: Is the design of high quality? Is it structurally strong, attractive, and well proportioned?
Material Cost: What was the total cost of the design? Was the team able to stay on or under budget?
Presentation: How well did the team communicate all aspects of the design to others?
Specifications
Performance
Team Collaboration
Design Quality/Aesthetics
Meets all specifications
Design performs consistently well
Every member of team contributed
Great design/aesthetics
On Budget ($140 or Less)
Great presentation/well explained
Good presentation/well explained
Poor presentation/explanation
No presentation/explanation
Over Budget ($146-155)
Significantly OverBudget ($156+)
Most members of team contributed
Good design/aesthetics
Average design/aesthetics
Poor design/aesthetics
Some members of team contributed
Design performs well often
Design is partially functional
Design does not work
Team did not work together
Meets most specifications
Meets some specifications
Does not meet specifications
Material Cost
Presentation
Points
Total Points
Proficient4 Points
Advanced5 Points
Partially Proficient3 Points
Not Proficient0 Points
/30
Grading Rubric
Slightly OverBudget ($141-145)
55-01218-200