Chair Lift Challenge
Driving Question: What components and materials can be used to create a
model ski lift?
Building Towards
PE MS-ETS1-2 Evaluate competing design solutions using a systematic process to
determine how well they meet the criteria and constraints of the problem.
PE MS-PS2-2 Plan an investigation to provide evidence that the change in an
object’s motion depends on the sum of the forces on the object and the mass of the
object.
Science and Engineering Practices
● Constructing Explanations and Designing Solutions- Apply scientific ideas or
principles to design, construct, and test a design of an object, tool, process or
system.
Disciplinary Core Idea: ETS1.B: Developing Possible Solutions
● A solution needs to be tested, and then modified on the basis of the test
results in order to improve it. There are systematic processes for evaluating
solutions with respect to how well they meet criteria and constraints of a
problem.
Disciplinary Core Idea MS-PS2.A: Forces and Motion
 The motion of an object is determined by the sum of the forces acting on it; if
the total force on the object is not zero, its motion will change. The greater
the mass of the object, the greater the force needed to achieve the same
change in motion. For any given object, a larger force causes a larger change
in motion.
Crosscutting Concept: Structure and Function
 Structures can be designed to serve particular functions.
Common Core State Standards
CCSS. Math.Practice.MP3
 Construct viable arguments and critique the reasoning of others.
CCSS.ELA-Literacy.SL.6.4
 Present claims and findings, sequencing ideas logically and using pertinent
descriptions, facts, and details to accentuate main ideas or themes; use
appropriate eye contact, adequate volume, and clear pronunciation.
CCSS.ELA-Literacy.SL.6.5
 Include multimedia components (e.g. graphics, images, music sound) and
visual displays in presentations to clarify information.
Prerequisites
In previous lessons, students should have engaged with the terms “force” and
“mass”.
Investigation 1: Introduction to the Challenge
Materials
 Image or video of a ski lift
 For each group: Ping-Pong ball, string, floral wire, pipe cleaners, bendable
aluminum wire, straws, paper towel tubes, paper clips, tape, balloons, glue,
string, foil, plastic wrap, pulley, other items available in the classroom.
Instructional Sequence
Begin the discussion by asking students to think about a very large hill or a
mountain. Ask students to brainstorm some methods of getting from the bottom of
the hill to the top. Encourage students to be creative and record their responses on
the board. (This initial brainstorm serves as a way to assess student thinking and prior
knowledge.)
Continue this discussion by presenting students with an image or video of a ski lift.
Ask students to use their prior knowledge and/or the image to think about how a
ski lift works. Ask students to independently create an annotated drawing of how
they think the lift works. (You can use the annotated drawings as an assessment tool.)
If a ski lift is not something your students can relate to, use the class discussion to elicit
some reasons why students can envision people or goods needing to get to the top of
the mountain and use that as the challenge scenario moving forward.
After students have had time to work, ask students to get into small groups and
share their annotated drawings with their group members.
Tell students that today they will be designing a chair lift. Instead of moving people,
they will be moving a Ping-Pong ball. The “mountain” is 2 ft. high and each lift must
be able to transport the ball "up the mountain" and "down the mountain" without
the ball dropping out of the chair they develop to hold the Ping-Pong ball.
Before students begin designing, present students with the materials that they can
use. Then, work as a class to devise a system for testing and evaluating the success
of each lift. Remind students that knowing the evaluation plan influences how
engineers design and build products and systems.
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Sample Evaluation Criteria and Constraints
After placing the ball in the chair, no hands can touch the ball.
You cannot tape the ball to the chair.
The ball must make it up to 2ft. before beginning its descent.
The ball must make it up and down again within two minutes in order for
the test run to be considered successful.
If the ball falls out, groups will be allowed one additional attempt.
Now, instruct students to work with their design team to create a new, more
detailed drawing of what their ski lift will look like and how it will function.
Students should submit their final design to you before building so that you have the
opportunity to identify potential issues they might encounter. This will also help
with materials management.
Investigation 2: Designing and Testing
Materials
 For each group: Ping-Pong ball, string, floral wire, pipe cleaners, bendable
aluminum wire, straws, paper towel tubes, paper clips, tape, balloons, glue,
string, foil, plastic wrap, pulley, other items available in the classroom.
Instructional Sequence
Give the teams time to build. The amount of time you can dedicate to this project is
up to you. Keep students on task by setting interim deadlines.
 Design Review: Midway through the building phase, have groups give brief
presentations to the class discussing their designs. Allow time for questions
from their peers.
After groups are done building, test each ski lift according the agreed upon
evaluation plan. As each group tests, all other groups should be taking note of the
design and success of their peers’ lifts. Encourage students to think about the
function that each materials plays in the lift system. Do certain materials lend
themselves to certain uses? (As an additional accommodation, you can create a
worksheet that will support students in recording their observations during testing.)
Once all groups have tested, ask each student to work independently to write down
three features or materials that seemed to contribute to the success of successful
designs as well as why they think this. (Use these responses as an assessment tool.)
Investigation 3: Redesigning and Testing
Materials
 For each group: Ping-Pong ball, string, floral wire, pipe cleaners, bendable
aluminum wire, straws, paper towel tubes, paper clips, tape, balloons, glue,
string, foil, plastic wrap, pulley, other items available in the classroom.
Instructional Sequence
Instruct students to return to their design groups. Tell students that iteration, the
process of refining and retesting a design, is an integral part of the engineering
process. Inform students that they will now have the opportunity to redesign and
retest their lifts using the results of investigation 2 to inform their designs.
If needed, remind students about the criteria and constraints of the challenge.
Use the same process as Investigation 2 to have students refine and retest their lifts.
In addition to testing the lift, each group should explain what changes they made to
their design as well explain why they made those changes.
After all student groups have tested, once again ask students what features seemed
to lead to successful lifts.
Investigation 4: Changing the Mass
Materials
 For each group: golf ball, container with water, paper towel tube, Styrofoam
tray, paper towels
 Observation Directions Worksheet
Instructional Sequence
Have students return to their design group. Tell students that the ski resort
companies often have to change the criteria by which they judge their ski lifts in
order to comply with changing safety standards. Inform students that instead of
carrying a Ping-Pong ball, they must now design a lift that can carry a golf ball up
and back down a 2 ft. “mountain”. The evaluation criteria should remain the same.
Ask students, “What are the differences between a golf ball and a Ping-Pong ball?”
(Response might include mass, texture, or size.)
Tell students that they will now work with their design teams to investigate the
differences further. Pass out the Observation Directions Worksheet, and instruct
students to follow the instructions. (As an accommodation for some students, you
may wish to go through the activities and worksheets as a class. Additionally, you can
add visuals to the worksheet.)
After students have had time to make and record observations, come back together
as a class, and ask groups to share out their observations. Help students focus in on
the idea that since the golf ball has greater mass, more force was needed to cause
the same change in motion than was required to move the Ping-Pong ball.
Investigation 5: Redesign and Presentations
Materials
 For each group: string, floral wire, pipe cleaners, bendable aluminum wire,
straws, paper towel tubes, paper clips, tape, balloons, glue, string, foil, plastic
wrap, pulley, other items available in the classroom.
 Presentation Rubric
Instructional Sequence
Inform students that they will now work with their design groups to use the data
they just gathered to inform thee redesign of their lift to accommodate a golf ball.
Before groups begin designing, ask each student to independently write a response
to the following prompt: “What changes do you need to make to your design to
accommodate a golf ball and why?” (Use this written response as an assessment tool.)
Have students return to their groups. Once again, have students submit a drawing
prior to building, and then allow students time to build. After all groups have built
their designs, students should follow the same protocol to test the lifts and record
results.
After all students have tested, tell students that they will work with their design
groups to prepare for short presentations. Review the Presentation Rubric as a
whole class before students break into their groups.