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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