Slinky Drop - (PHENOMENON)

Derek Muller - Veritasium
Type Category
Instructional Materials
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.



This is the first in a series of 3 video clips. In this first video, a slinky is held in the air by one end.  The question is asked: when the slinky is let go, will the top fall first, will the bottom fall first, will the slinky “accordion” together first, or will the whole slinky fall at the same time?  Students are asked to make a prediction.  The result is not given in this video, but is instead seen in the second video, “Slinky Drop Answer”, at  “Slinky Drop Answer” also posits another question:  what if a weight (a tennis ball) is attached to the bottom of the slinky?  The result is shown in the third and final video, “Slinky Drop Extended”,, which also relates the phenomenon to other applications in sports. (A fourth video, with background for teachers, is available on the Veritasium website,

Intended Audience

Educator and learner
Educational Level
  • Middle School
  • Grade 8
  • Grade 7
  • Grade 6
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

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.

Clarification Statement: Emphasis is on balanced (Newton’s First Law) and unbalanced forces in a system, qualitative comparisons of forces, mass and changes in motion (Newton’s Second Law), frame of reference, and specification of units.

Assessment Boundary: Assessment is limited to forces and changes in motion in one-dimension in an inertial reference frame and to change in one variable at a time. Assessment does not include the use of trigonometry.

This resource was not designed to build towards this performance expectation, but can be used to build towards it using the suggestions provided below.

Comments about Including the Performance Expectation
To understand the phenomenon, the students must consider how multiple forces are acting on the slinky. This phenomenon may function well near the end of a unit about forces, once students are familiar with the idea of multiple forces acting at once. The students will also need to be familiar specifically with the forces of tension and gravity. Students without this knowledge will not be able to explain for themselves what is going on or why. The first video in the series could also be shown without its two follow-ups, and students could try the experiment for themselves, then be asked to explain the results they got. Alternatively, the second phase (in videos 2 and 3) in which a tennis ball is attached to the bottom of the slinky, could be used to assess understanding after the first phase has been discussed.

Science and Engineering Practices

This resource was not designed to build towards this science and engineering practice, but can be used to build towards it using the suggestions provided below.

Comments about Including the Science and Engineering Practice
Students should be asked to not only “guess” what will happen when the slinky is let go in video 1, but to explain their reasoning. A scientifically correct explanation takes into account the relationship between tension and gravity acting on the slinky.

Disciplinary Core Ideas

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
To solve the question posited in the first video, watchers will need to consider the forces acting on different parts of the slinky, and how they interact. A force diagram and explanation are included in the second video, which may be watched after students have shared their answers and reasoning, or perhaps after students have tried an experiment for themselves. The second phase of the phenomenon involves adding more mass to the end of the slinky, but the videos do not address the idea of the larger mass requiring a larger force of gravity or tension. Magnitudes of forces are not addressed.

Crosscutting Concepts

This resource was not designed to build towards this crosscutting concept, but can be used to build towards it using the suggestions provided below.

Comments about Including the Crosscutting Concept
This CCC can be addressed by asking the students “Why isn’t the slinky changing its motion while the man is holding it?” This gets at the idea of balanced forces, and the teacher can expand that to the concept of dynamic equilibrium, or multiple actions (in this case forces) balancing each other out. The question can also prepare students for the video’s own question of what will happen when the slinky is dropped, by priming the students to be considering multiple forces.

Resource Quality

  • Alignment to the Dimensions of the NGSS: Not applicable. This resource is a phenomenon.

  • Instructional Supports: Not applicable. This resource is a phenomenon.

  • Monitoring Student Progress: Not applicable. This resource is a phenomenon.

  • Quality of Technological Interactivity: While the resource does not require interactivity, it does require YouTube access. If your school prohibits this, the videos can also be found on the Veritasium website, though they are not “connected” to each other as they are on the YouTube site. Slinky Drop: Slinky Drop Answer: Slinky Drop Extended: