pulley - kid spark education · in this example, which also confirms that this pulley system has a...

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v2.1

Pulley

Curriculum Packetv2.1

Applications in Design & Engineering: Simple Machines

IntroductionThis Kid Spark lesson will use the following steps to learn about the pulley.

Click here to explore the entire Kid Spark Curriculum Library.

Key Terms

Simple Machine: A device that transmits or modifies force or motion.

Pulley: A simple machine consisting of a wheel with a grooved rim in which a pulled cable can change the direction of the pull an thereby lift a load.

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 of a pulley.

Understand how a pulley redirects motion and creates mechanical advantage.

Calculate the amount of mechanical advantage in a pulley system.

Modify a pulley system to increase mechanical advantage.

Design and engineer a custom pulley system.

Elements of a pulley Purpose of a pulley system Real world applications Creating mechanical advantage with pulleys

1. Learn 2. Build & Modify

3. Design & Engineer

Build a fixed pulley system Build a movable pulley system Modify a pulley system from 2:1 to 3:1 mechanical advantage

Design & engineer a custom pulley system to solve a challenge

Kid Spark Mobile STEM Lab

Engineering Pathways

*4 Students Per Lab

or or orYoung

Engineers

*4 Students Per Lab

SnapStack

*4 Students Per Lab

AdvancedProjects

*4 Students Per Lab

2

Building BasicsThe following tips will be helpful when using Kid Spark engineering materials.

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/Disconnect Smaller Engineering Materials:

Smaller engineering materials use a tab and opening system to connect. Angle one tab into the opening, and then snap into place. To disconnect, insert key into the engineered slot and twist.

Snapping Across Openings:

Materials can be snapped directly into openings or 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 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

Measuring:

The outside dimensions of a basic connector block are 2 cm on each edge. This means the length, depth, and height are each 2 cm. To determine the size of a project or build in centimeters, simply count the number of openings and multiply by two. Repeat this process for length, depth, and height.

2cm

2cm

4cm 4cm

4cm

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The PulleyA pulley is a simple machine that consists of a wheel and axle with a groove cut into the edge of the wheel to accept a cable. The pulley allows the cable to be attached to a load and transfers the downward pull of the cable to raise the load.

PurposesPulleys can be used to redirect motion or to reduce the amount of effort needed to raise a load by creating mechanical advantage.

Redirecting Motion

In a single fixed pulley system (example 1), the amount of effort needed to raise the load must be more than the load itself. For example, if the load was 100lbs, a force greater than 100lbs would be needed to raise the load. A single fixed pulley system is only used to redirect motion. If a user pulls down on one end of the cable (Effort), the other end (Load) will raise up an equal distance in the opposite direction.

Creating Mechanical Advantage

Pulleys are used to reduce the amount of effort needed to raise a load by creating mechanical advantage. To create mechanical advantage in a pulley system, a movable pulley must be attached directly to the Load (example 2). A movable pulley system trades increased distance for reduced Effort.

Real World ApplicationsPulleys are used in many different ways to make work easier. Here are some real world examples.

Learn

Example 1 - Single Fixed Pulley

FixedPulley

Effort Load

Example 2 - Movable Pulley

FixedPulley

Effort

Load

MoveablePulley

Block & Tackle Water Well Crane Truck Flag Pole Belt Pulleys

Wheel

Cable Axle

4

Build & Modify

InstructionsFollow the step-by-step instructions to build a pulley system.

4x Block

2x Beam

3x Half Beam

2x Riser

2

3x Beam

2x Half Beam

3x Single Snap Block

3

1x Block

3x Beam

1x Half Beam

3x 60° Block

3x 30° Block

1

5

Build & Modify


3x Block

4x Half Beam

2x 60° Block


2x Riser

6

1x String Block

5x Pulley

4 5

6

Build & Modify


7

4x Trailer Hitch

10 BlocksSeparating

Markers

5 BlocksSeparating

Markers

Cut a piece of string that is 40cm long. Feed each end of the string through the single snap blocks as shown. Lay string on top of the red connector blocks and snap into place. Once connected, place string of weights over fixed pulleys.

2x Block

2x Snap-In Wheel


Assemble two weights using the listed components. Cut a piece of string that is 50cm long. Tie a knot in one end of the string and place knot in string block to secure into place. Feed other end of the string through the fixed pulleys and movable pulley (weight 2) as shown. Connect string to weight 1 to secure in place.

Note: Adjust string if necessary so that when weight 1 is resting on frame, top of weight 2 is even with top markers.

2x Block

2x Snap-In Wheel

1x Pulley


String Block

Top Markers

Weight 1

Weight 2

9

8

Top Markers:Upside-Down

Middle/Bottom Markers: Right-Side Up

7

Build & Modify

Testing Pulley SystemFollow the instructions below to test both sides of the pulley model.

Turn the pulley system so that you can test the fixed pulley system. Observe how the weights balance each other out. Pull down on Weight 1 (Effort) and observe how Weight 2 (Load) moves an equal distance in the opposite direction.

Weight 1Effort

Weight 2Load

Fixed Pulley Fixed PulleyFixed Pulley (Redirecting Motion)

Turn the pulley system around to the side with the movable pulley. Lift Weight 1 (Effort) until the top is even with the top markers. At this point, Weight 2 (Load) should be even with the middle marker. Let go of Weight 1 (Effort) and observe how it is able to raise Weight 2 (Load) to the top markers.

Weight 1Effort

Weight 2Load

MiddleMarker

LowMarker

TopMarkers

Movable Pulley (Mechanical Advantage)

Fixed Pulley System

FixedPulley

Effort Load

FixedPulley

Movable Pulley System

Effort

Load

FixedPulleys

MoveablePulley

FixedPulley

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Understanding Mechanical AdvantageThe main purpose of a simple machine is to make work easier. This means either redirecting motion 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.

Calculating Mechanical Advantage

Calculating the mechanical advantage in a pulley system can be done by dividing the distance the effort travels by the distance the load travels. If the pulley system has a movable pulley, the number of strings connected to the movable pulley can also be used to determine the mechanical advantage.

Modify: Pulley SystemNow that you have built a pulley system that has a mechanical advantage of 2:1, slightly modify the system to increase the mechanical advantage to 3:1.


In the movable pulley system, Weight 1 (Effort) travels a distance of 10 blocks (20 cm). Weight 2 (Load) travels a distance of 5 blocks (10 cm). Divide 20/10 and this will give a mechanical advantage of 2:1. This means that for every two units of measurement the effort travels, the load will travel one unit of measurement in the opposite direction. There are two strings connected to the movable pulley in this example, which also confirms that this pulley system has a mechanical advantage of 2:1. This pulley system is able to output a greater force than the input force that was applied to it.

Fixed Pulley System

In the fixed pulley system, if Weight 1 (Effort) is pulled down, then weight 2 will raise and equal amount in the opposite direction. Divide 8/8 and this will give a mechanical advantage of 1:1. This means that for every unit of measurement the effort travels, the load will travel an equal unit of measurement in the opposite direction. This demonstrates how there is no mechanical advantage in a fixed pulley system. In order to raise one of the weights, extra effort or mass would be needed to overcome the mass of the load.

Movable Pulley Systems

# of strings connected to

movable pulley

MechanicalAdvantage=

Weight 1Effort

Fixed Pulley System

Weight 2Load


Weight 1(Effort)

Weight 2(Load)

Effort - 20cmLoad - 10cm = 2 = 2

2 of strings connected to

movable pulley

Build & Modify

10 cm

10 cm Weight 1Effort

Weight 2Load

Distance Formula

Distance effort travels Distance load travels

MechanicalAdvantage =

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Design & Engineering Challenge: Pulley System

In this challenge, each team must design and engineer a custom pulley system. Read carefully through the design brief below, then use the Design & Engineering Process to develop a solution to the challenge.

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.

1x Riser

1xBlock

4x Snap-In Wheel

1x Corbel


Go-Cart Assembly

Design & Engineer

Design Brief: Scenario

You have just inherited a motorized go-cart from your uncle. It is in good shape, but needs an oil change before you can ride it. The drain plug for the oil is underneath the go-cart frame so it is difficult to change the oil while it is on the ground.

Design & Engineering Challenge

Your design challenge is to design and engineer a pulley system that can raise and lower a go-cart so routine maintenance can be done on it.

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 Kid Spark Design & Engineering process to design, prototype, and refine a custom pulley system. Teams will be responsible for written documentation in the student engineering workbook.

3. Sub-Challenge: The pulley system must raise the go-cart at least 18cm off of the ground.

4. Sub Challenge: The pulley system must be able to carefully lower the go-cart back to ground level.

5. Sub-Challenge: The pulley system must feature a safety locking pin to keep the rope or cable in place while being worked on.

6. The pulley system must be aesthetically appealing.

7. Sub-Challenge: The pulley system must create mechanical advantage.

8. With each building component costing $2, the pulley system must cost less than $120. (The components in the go-cart do not count towards the budget of $120).

9. Each team will be required to effectively explain all aspects of brainstorming, prototyping, testing and improving the custom pulley system. Teams will also be responsible for explaining how the pulley system works and creates mechanical advantage.

Design and Engineering Process Student Engineering Workbook

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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 ($120 or Less)

Great presentation/well explained

Good presentation/well explained

Poor presentation/explanation

No presentation/explanation

Over Budget ($130-140)

Significantly OverBudget ($141+)

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 ($120-130)

55-01191-201

pulley - kid spark education · in this example, which also confirms that this pulley system has a...

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