Inertia Tower

Perkins School for the Blind Stu Grove
Type Category
Instructional Materials
Experiment/Lab Activity , Lesson/Lesson Plan




In these activities, students explore the concept of inertia.  They try to keep a block tower standing when cards are pulled from between the blocks, then compare with what happens when they try the same activity with lighter objects such as paper cups.  A variation is included in which students pull a large cardboard box a certain distance while being timed, then try again as people of different masses sit inside the box.

Intended Audience

Educational Level
  • Grade 8
  • Grade 7
  • Grade 6
  • Middle School
Access Restrictions


Performance Expectations

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.



This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
This activity would work well as an investigation midway through a study of forces, mass and motion. It will be helpful for students to be familiar with the concept of balanced forces vs. unbalanced forces, to help them construct explanations for the phenomenon of inertia. Students might already be familiar with ideas about friction, or the activity could lead to the idea of friction, via the question of “Why do the blocks move when we pull the card slowly but not when we pull it quickly?” The variation activity is useful to include as it expands the focus from inertia to acceleration, and the effect of mass on acceleration. Students do not plan their own investigation in this lesson, so while this activity encourages them to consider variables and collect data, it is not suitable as an assessment for this Performance Expectation.

Science and Engineering Practices


Comments about Including the Science and Engineering Practice
The scientific question offered for investigation is a rather general “What’s going on here?” which makes this an appropriate phenomenon for a lesson about inertia. Students are asked to gather qualitative data via observation. They are asked to observe the blocks’ behavior, and to compare it to the behavior of paper cups in the same setup. The variation activity has students collect quantitative data about the amount of time required to move a box a certain distance. This data should be used as a springboard to explain ideas of inertia and forces. The relationship between force and acceleration is also touched upon.

Disciplinary Core Ideas


Comments about Including the Disciplinary Core Idea
Observation of the “blocks” phenomenon is intended to lead students via discussion to the idea of inertia. . The comparison of blocks to cups addresses the relationship between mass and force, and the variation brings acceleration (change in motion) into the mix. It is recommended that students experience the phenomenon before being introduced to the vocabulary at the beginning of the lesson. The first part of the Core Idea (motion related to the sum of forces) could be made clearer by asking students to identify the forces working on the blocks and to determine if the forces are balanced or unbalanced.

Crosscutting Concepts


Comments about Including the Crosscutting Concept
As they come to grips with inertia, students are asked to compare the behavior of the heavier (dekagram) blocks with the lighter (gram) cups. They also compare motion of a light (grams) box to one with a heavy (many kilograms) mass inside. This leads to the idea that scaling the mass up or down changes the behavior of the system. Students could be asked - which system is more stable? Which is more likely to change? Why? Time is the dependent variable in the “box” variation, and its role could be further examined by asking students to pull the cards from the blocks slowly then quickly, then asking students to explain or figure out why the blocks behaved differently with the different speeds.

Resource Quality

  • Alignment to the Dimensions of the NGSS: The lesson centers around exploration of phenomena leading to ideas about inertia and about relationships between mass, force and acceleration. Students collect qualitative and quantitative data then use that data to make sense of the core ideas. The cross-cutting concept of stability and change, though not highlighted, is present throughout the activities, which are asking students to look at motion vs. staying still. The lesson plan as written tells the teacher what was different between the blocks and the cups. It will be important for the teacher to ask instead of tell the students: what was different? Why was the activity harder with the cups? Why might the heavier box have moved more slowly?

  • Instructional Supports: The phenomenon is offered as a challenge, and is engaging for students. Safety measures for the activities are mentioned. The lesson is lacking in detail about how students should share their knowledge and ideas. A discussion would work if this activity is early in students’ learning about forces. Students with more understanding could be asked to create models to explain the phenomena. This lesson’s strength is in its scope for differentiation. The activities were specifically designed for blind or visually impaired students and for students of varying fine motor skills. Suggestions are offered for making the blocks-and-cups phenomenon either an individual or a group challenge. Suggestions are included for adapting to varying physical abilities.

  • Monitoring Student Progress: The lesson offers brief suggestions about what to have the students observe, but does not follow up with what to have them do with their observations. A description of what happened with the writer’s students implies discussion points, but does not give specific details for assessment. By noting the points that the writer’s students observed, and how they led to discussions, teachers could prepare or design a formative assessment for their own classes.

  • Quality of Technological Interactivity: - none -