Classbox
Classic STEM Project: Pulleys
PhysicsEngineering Design

Classic STEM Project: Pulleys

Grades 3–8
1 hr 30 min
10 steps
NGSSSTELISTE

Standards Alignment

NGSS

  • 3-PS2-1: Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object.
  • 3-5-ETS1-2: Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
  • 3-5-ETS1-3: Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
  • 3-5-ETS1-1: Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.
  • MS-ETS1-2: Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
  • MS-ETS1-3: Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.
  • MS-ETS1-4: Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved.

STEL

  • 3-5-1H: Design solutions by safely using tools, materials, and skills.
  • 3-5-2F: Describe how a subsystem is a system that operates as a part of another, larger system.
  • 3-5-2J: Demonstrate how tools and machines extend human capabilities, such as holding, lifting, carrying, fastening, separating, and computing.
  • 6-8-7Q: Apply the technology and engineering design process.
  • 6-8-7U: Evaluate the strengths and weaknesses of different design solutions.

Showing 12 of 19 standards.

Lesson Steps

1

Overview

Not listed

Welcome to the Pulley STEM Classic! In this project, you will learn that pulleys are found in many everyday applications and often help provide a mechanical advantage.

Teaching tips

Welcome to the Pulley STEM Classic!

 

First, let's talk material. Here is a link to the material list. These materials are enough for 24 students working in 8 groups of 3. 

There is an extra block pulley for each group. This is actually one extra than what students will need for the regular project. But, if you have students doing the optional extension, they may want more blocks available. Perhaps you could do the extension as a station and have only one group working on the pully extension at a time. This would give them plenty of materials.

As for the rope, I prefer using 550 paracord. I made a short video on how I like to fuse the ends. 100 feet of rope divided into 8 groups gives you 12.5 feet per group. I actually like to have twelve feet for the pulley part and six inches for tying the mass/weight to the end of the pulley. The carabiners are really helpful for this too. Paracord comes in many colors, but I prefer black because we are using chalk to measure out the amount of rope being pulled out.

For the horizontal support, I used a 2x2 furring strip. You can support this between two chairs or between two tables. For hooks, I recommend spacing them about 8" apart, 4" on each side of the center of the support. the 1/16" drill bit only needs to go in about 1/2 to 3/4" to drill the pilot hole. 

 

Note: This project does cover some more advanced concepts like force, displacement, and work. While it would be great to introduce students to these topics, if you do not think these are age-appropriate, you can compare force needed to lift and length of rope for each pulley system. 

 

2

Vocabulary and Tools

10 min

In this section, you will learn about vocabulary related to pulleys and the tools used in this project.

Vocabulary:

Effort: the force that is applied to pull the rope
Load: the mass that is lifted or supported on the pulley
Mechanical Advantage: the factor by which a simple machine reduces the effort needed to lift an object
Newtons: a unit of force
Displacement: the distance the object moves (can be rope or the mass!)
Work: measured in joules; the force (in Newtons) multiplied by displacement (in meters).

 

Tools: 

Pulley Block: the pulley block is a simple machine that has a grooved wheel which allows a rope to move through it. The swivel allows it to turn freely. Make sure you are putting the rope over the wheel to take advantage of the wheel! Note the support bar across the bottom (opposite the swivel). This will come into use later as an attachment point! 

Spring Scale: This scale measures in both grams and Newtons. Below is a video discussing how to zero your spring scale and where to read your measurements!

 

 

 

 

 

 

 

 

 

STEM Classics: Zero the Spring Scale by Jim Stith

 

Now that we have learned a little bit about the tools and vocabulary, let's look at a practical application of a pulley!

Teaching tips

In this section, students will learn about vocabulary related to pulleys and the tools used in this project.

3

Why use Pulleys?

10 min

In this step, you will learn about how a pulley is set up as well as some basic applications for pulleys. 

Now that we have learned a little about pulleys, let's look at how to set up our pulleys and what data we need to collect!

Teaching tips

In this step, students will learn about how a pulley is set up as well as some basic applications for pulleys.

After the video, you can check for understanding by having students list examples of pulleys from the video.

4

Data to Collect

10 min

In this step, you will learn about the basic setup, the measurements you will need, and some calculations to help show the effectiveness of the pulleys. 

In each step, consider:" What is the force needed (and rope length required) to lift a (insert mass here) X distance?"

To collect and organize your data, set up a table like this in your notebook:

  Single Fixed Pulley Moveable Pulley Compound Pulley Block and Tackle DIY Pulley
Force of Mass (N)          
Force needed to lift mass (N)          
Length of rope needed to lift mass (Displacement) (m)          
Height mass was lifted (Displacement) (m)          
Work on mass side (J)          
Work on the rope side (J)          
Number of Load Lines          
Mechanical Advantage           

(N) means the units here will be in Newtons
(m) means the units here will be in meters
(J) means the units here will be in Joules (Newtons * meters)
Force of Mass means the force of the mass when it is hanging straight from the spring scale
Number of Load Lines refers to the number of ropes that support the mass/load in an upward direction
Mechanical advantage is the reduction of force due to using a pulley. For example, if your mass is exerting 10 Newtons and your scale says 10 Newtons, then you have a 1:1 ratio, so no real advantage. But if your scale is reading 2.5 Newtons, then you have a 4x mechanical advantage since you're lifting 4 times as much force as the effort you're exerting!

STEM Classics: Basic Setup and Force and Work by Jim Stith

Teaching tips

In this step, students will learn about the basic setup, the measurements they will need, and some calculations to help show the effectiveness of the pulleys. 

 

 

5

Single Fixed Pulley

10 min

In this step, you will learn to set up and test a single fixed pulley.

Remember, in each step, consider:" What is the force needed (and rope length required) to lift a (insert mass here) X distance?"

STEM Classics: Single Fixed Pulley by Jim Stith

After you set up and test your single fixed pulley, make sure you record your data in your table! Next, we will look at a movable pulley!

Teaching tips

In this step, students will learn to set up and test a single fixed pulley.

6

Movable Pulley

10 min

In this step, you will learn to set up and test a movable pulley.

Remember, in each step, consider:" What is the force needed (and rope length required) to lift a (insert mass here) X distance?"

STEM Classics: Movable Pulley by Jim Stith

After you set up and test your movable pulley, make sure you record your data in your table! Next, we will look at a compound pulley!

Teaching tips

In this step, students will learn to set up and test a movable pulley.

7

Compound Pulley

10 min

In this step, you will learn to set up and test a compound pulley.

Remember, in each step, consider:" What is the force needed (and rope length required) to lift a (insert mass here) X distance?"

STEM Classics: Compound Pulley by Jim Stith

After you set up and test your compound pulley, make sure you record your data in your table! Next, we will look at a Block and Tackle pulley!

Teaching tips

In this step, students will learn to set up and test a compound pulley.

8

Block and Tackle Pulley

10 min

In this step, you will learn to set up and test a block and tackle pulley.

Remember, in each step, consider:" What is the force needed (and rope length required) to lift a (insert mass here) X distance?"

STEM Classics: Block and Tackle Pulley by Jim Stith

After you set up and test your block and tackle pulley, make sure you record your data in your table! Next, we will draw some conclusions from the data.

Teaching tips

In this step, students will learn to set up and test a block and tackle pulley.

9

Reflection

10 min

In this step, you will reflect on your learning during the Pulley STEM Project.

1. What parts of this project were easy? Which parts were more difficult?

2. Did you run into any problems while constructing your pulleys? Were you able to find a solution on your own? If not, where did you find help with a solution?

3. What did you learn about pulleys?

4. What did you learn about force, displacement, and/or work?

5. From your testing with the pulleys, what configuration(s) needed the least effort to lift the mass?

6. From your testing with the pulleys, how did the work on the rope side of the pulley (force from the spring scale multiplied by displacement [length of rope]) and the work needed to lift the mass (force of gravity on the mass multiplied by displacement [vertical lift]) compare?

7. How does the number of load lines affect the effort needed to lift a mass? What increases significantly with the addition of additional load lines?

8. As a result of this project, please share one new idea or new question you may have come up with or encountered.

Teaching tips

In this step, students will reflect on their learning during the Pulley STEM Project.

Note: This would make a great exit ticket!

10

Optional Extension: DIY Pulley System

10 min

In this optional step, you will design a pulley system to meet a customer's needs.

You are the owner of (insert your name here)'s Bicycle Emporium and a customer purchased a fancy new e-bike from your store. After taking a celebratory ride around the parking lot, the customer says, "This bike is great, but I don't know if I have space in my garage for a new bicycle!."

You then have a flash of brilliance! You remember about pulleys! You can help the customer design a pulley system to raise the bike from the garage floor to hang it under the rafters. The customer says, "That's great! I have a ton of overhead space we can use!"

The customer gives you the details and says they will come back tomorrow for the pulley instructions.

You must design a pulley system that meets these requirements:

1. The system must lift a 30-kilogram e-bike (and yes, they do get pretty heavy).
2. The system must lift the e-bike 5 meters from the garage floor to the rafters way overhead.
3. The system must not require more than 50 Newtons of effort to lift the bike (your customer has a shoulder injury).

You must:

1. Draw out the system to meet the customer's needs. Identify the mass (bike), load lines, pulleys, etc.
2. Calculate the amount of rope necessary to hoist the bike to the 5-meter height.
3. Calculate the amount of effort (force) needed to hoist the bike with your pulley configuration.
4. Calculate the amount of work needed to hoist the bike. 

Teaching tips

In this optional step, students will design a pulley system to meet a customer's needs.

This would be fun to assess as a presentation. The students could showcase their pulley system and show how it addresses the customer's needs given the particular constraints provided. 

Just as a reminder, Force equals mass times acceleration. So the bike is experiencing 9.8m/s of acceleration just by sitting on the ground. Its mass is 30kg, so the force is about 294 Newtons.

Student pulleys must overcome that force. However, since the customer cannot pull down with the force needed to hoist the bike with any of the pulley systems that the students have investigated in the lesson, they must draw on what they have learned to design a pulley system to multiply the customer's force to raise the bike.

Materials

  • Single pulley block with carabiner — 3 per group
  • 550 paracord (feet) — 12.5 per group
  • Spring scale (grams/Newtons) — 1 per group
  • Chalk — 1 per group
  • Eye screw — 2 per group
  • 2x2 in x 8 ft furring strip (horizontal support) — 4 per classroom
  • 1/16 in drill bit / drill for pilot holes
  • Saw for cutting 2x2s
  • Meter stick
  • Mass (under 2 kg) — 1 per group

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