Invisible Forces Mystery 3: How Can You Go Faster Down a Slide?

Mystery Science
Type Category
Instructional Materials
Activity , Experiment/Lab Activity , Lesson/Lesson Plan
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



“How Can You Go Faster Down a Slide?  is one of four mysteries that comprise a "Mystery Science" unit on forces and their interactions.  Students are posed the driving question: How can you go fastest down a slide?  Students then investigate friction as an oppositional force, its relationship to different material properties, and its effect on the downward motion of objects. The resource can be used even without a slide nearby.

Intended Audience

Educator and learner
Educational Level
  • Grade 3
Access Restrictions

Available by subscription - The right to view and/or download material, often for a set period of time, by way of a financial agreement between rights holders and authorized users.

Performance Expectations

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.

Clarification Statement: Examples could include an unbalanced force on one side of a ball can make it start moving; and, balanced forces pushing on a box from both sides will not produce any motion at all.

Assessment Boundary: Assessment is limited to one variable at a time: number, size, or direction of forces. Assessment does not include quantitative force size, only qualitative and relative. Assessment is limited to gravity being addressed as a force that pulls objects down.

This resource appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
At the outset of the mystery, construction tips are provided for making a model of a slide as well as the sliders. Sliders are pennies taped to pieces of cardboard to represent people sliding down the slide. The first two investigative questions are given to initiate the inquiry and establish the expectations for making and recording observations. In Activity 1, students are then given the opportunity to ask and investigate their own questions. In Activity 2, students will plan and conduct the investigative procedure to answer the question: Which materials have the most friction and which materials have the least friction? As the Performance Expectation is for students to plan their own investigations, it is recommended that the video for this activity be used for teacher information only. Also, as the recording sheets are editable, it is recommended that the “if you get stuck, think about..” be deleted, with ideas for investigation discussed as a class if teacher observations indicate the students are struggling in that regard. To more fully address this Performance Expectation, it is suggested that the movement of the sliders be discussed in terms of the opposing forces acting on the sliders, such that when the force of gravity is greater than the frictional forces opposing it, the forces are unbalanced and the object slide downward. Conversely, when the forces are balanced, there is “zero net force” and the object remains stationary.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
In Activity 2 the video introduces the concept of fair tests and demonstrates two ways a fair test can be conducted, but then proceeds to say that there is no single way to achieve a fair test and encourages students to decide on the way they would fairly conduct their investigation. No mention is made about controlling the slide length and teachers will need to ensure this is addressed as students plan their investigation. To more fully address this practice the importance of replicable trials should also be introduced, and the recording sheet edited to accommodate multiple trials for each variable tested.

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Observational data provides the primary evidence to explain how friction affects the motion of objects sliding downhill. The use of slow motion video would be a great way to provide recorded data of the trials as they are conducted. If the student chooses to conduct the investigation by elevating "ramp 1” for each trial then measurement would also be involved and factor in the explanation of the phenomena. If opting to forego measurement, the use of standard sized blocks of some kind are recommended over the use of books, which are a potentially uncontrolled variable in the investigation.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
Through the video tutorial students will learn that no material is completely smooth, and that an object in motion across a surface will exert frictional or oppositional forces on each other. This will be confirmed through the investigations as students observe that objects with smoother surfaces result in less frictional force, enabling a stronger (faster) slide downhill.

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
Through their investigations students will observe that the steeper the slide, the greater the gravitational force and the stronger the downhill slide of the objects. They will also observe that the objects with the smoothest surface creates the least frictional or oppositional force, also enabling a stronger downhill slide. To explicitly align to this Disciplinary Core Idea, the various forces should be discussed in terms whether they result in balanced or unbalanced forces acting on the objects and its resulting effect on the object’s motion.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
Students will conclude this investigation by making claims, and the cause and effect relationships of forces on the motion of objects will be imbedded in their evidence. For example, if the student claims that the sandpaper has the most friction, evidence to support the claim will likely include that sandpaper was observed to have the roughest surface (cause) creating the most frictional force and resulting in the shortest slide downhill. For this resource to explicitly align to this crosscutting concepts, these cause and effect relationships need to be explicitly stated in their evidences and identified in their discussions as a class.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This mystery provides grade-appropriate elements of the three dimensions that enable students to make sense of how frictional forces affect motion. Students are given the opportunity to plan and conduct their own investigations, making observations to produce data that serve as the basis for evidence to explain the phenomena. They are also enabled to construct explanations through claim making that is supported by evidence. To more rigorously align this mystery to the dimensions of the NGSS, it is recommended that the concept of balanced and unbalanced forces be more explicitly applied as they conduct their investigations. It is also recommended that the students explicitly identify a cause and an effect when describing the force and motion relationships they have discovered.

  • Instructional Supports: The resource's format easily enables the scaffolding of instruction, allowing for pauses to discuss, and ability to revisit previously viewed segments. Students engage in a meaningful scenario that provides students with a purpose for making sense of phenomena. It identifies and builds on students' prior knowledge about slides and provides opportunities for students to express, represent, and justify their ideas in written form. Increased opportunity to share and discuss observations and thinking as a class should be embedded throughout the activity. Guidance to support differentiated instruction is not provided, however the mystery is fairly well scaffolded with numerous visual examples and simple explanations. As this is an online resource, it enables students to revisit the content multiple times. Students who are struggling may benefit from actual experiences on a playground slide. The Friction and Shoes activity from NCSU’s Science House is suggested for students with high interest or are exceeding the performance expectation. This resource also has an Optional Extras section that provides additional instructional support. It includes an End of Mystery Assessment, two videos, a reading selection, and two extension activities. The assessment is editable, and it is suggested that for item #1 students might benefit from examining actual samples of the materials with a hand lens, drawing each surface based on their observations, then making a claim supported by evidence as to which material would slide downhill the fastest.

  • Monitoring Student Progress: An "End of Mystery Assessment" is provided. It is recommended that students revisit the anchoring phenomenon and make a claim supported by evidence as an assessment. The videos provided in the Optional Extras section could also be used as a summative assessment piece as it asks students to figure out what is going on in the video, essentially asking the student to apply their knowledge to make a claim and provide evidence. Student engagement in the investigations elicits direct observable formative evidence of student learning, and the investigation recording sheets provide additional formative assessment information. It is suggested that opportunities for peer and teacher feedback be embedded into this mystery.

  • Quality of Technological Interactivity: Mystery Science is an online resource with links to many other resources, some of which are interactive for students to engage in.