Source sheet

Sources for “Why Copper Slows a Falling Magnet”

Every factual claim in the video, with the evidence we read at the source: who published it, where exactly it is stated, when we checked it, and what it does not support.

Evidence reviewed: 11 October 2026 · 9 claims · 3 sources

Claim A01

A strong magnet dropped through a suitable copper pipe can be slowed down considerably and take seconds to fall through.

Electromagnetic braking: A simple quantitative model

Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics · September 2006 · DOI 10.1119/1.2203645

Evidence level: Level 2
Location: p. 815, introduction; pp. 816–817, experiment
Checked: 11 October 2026
Limitation: The source gives no fall time for the demonstration shown in the video; not every magnet and pipe combination brakes equally.

Lenz’s Law – Tubes and Magnets

University of Iowa, Physics & Astronomy · Not stated; accessed 11 October 2026 · https://instructional-resources.physics.uiowa.edu/5k2025-lenzs-law-tubes-and-magnets

Evidence level: Level 2
Location: section “Procedure”
Checked: 11 October 2026
Limitation: The source gives no fall time for the demonstration shown in the video; not every magnet and pipe combination brakes equally.

Claim A02

The moving magnet changes the magnetic flux; the voltage this induces in the conducting pipe drives circular currents. Dividing the pipe into rings is a model.

Electromagnetic braking: A simple quantitative model

Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics · September 2006 · DOI 10.1119/1.2203645

Evidence level: Level 2
Location: p. 815, section II “Theory”; Fig. 1
Checked: 11 October 2026
Limitation: The ring picture is qualitative: it does not show a measured field distribution, and no power supply is connected to the pipe.

Magnet fall inside a conductive pipe: motion and the role of the pipe wall thickness

G. Donoso, C. L. Ladera, P. Martín; European Journal of Physics · 27 May 2009 · DOI 10.1088/0143-0807/30/4/018

Evidence level: Level 2
Location: pp. 856–858, §1.1; Fig. 2, Eqs. 1–4
Checked: 11 October 2026
Limitation: The ring picture is qualitative: it does not show a measured field distribution, and no power supply is connected to the pipe.

Claim A03

The induced currents produce a magnetic force that opposes the motion; the current flows in opposite directions where the magnet approaches and where it moves away.

Electromagnetic braking: A simple quantitative model

Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics · September 2006 · DOI 10.1119/1.2203645

Evidence level: Level 2
Location: p. 815, section II “Theory”
Checked: 11 October 2026
Limitation: Applies to the described setup with a conducting, non-ferromagnetic pipe. The effect is not antigravity.

Magnet fall inside a conductive pipe: motion and the role of the pipe wall thickness

G. Donoso, C. L. Ladera, P. Martín; European Journal of Physics · 27 May 2009 · DOI 10.1088/0143-0807/30/4/018

Evidence level: Level 2
Location: pp. 856–859, model section
Checked: 11 October 2026
Limitation: Applies to the described setup with a conducting, non-ferromagnetic pipe. The effect is not antigravity.

Claim A04

In the slow-fall regime described, the magnet first accelerates and then approaches a terminal velocity once the magnetic force balances its weight.

Electromagnetic braking: A simple quantitative model

Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics · September 2006 · DOI 10.1119/1.2203645

Evidence level: Level 2
Location: p. 815, section II “Theory”
Checked: 11 October 2026
Limitation: The magnet does not fall at exactly constant speed from the moment it is released; the ends of the pipe and other regimes are excluded.

Magnet fall inside a conductive pipe: motion and the role of the pipe wall thickness

G. Donoso, C. L. Ladera, P. Martín; European Journal of Physics · 27 May 2009 · DOI 10.1088/0143-0807/30/4/018

Evidence level: Level 2
Location: pp. 859–860, §2; p. 865, Fig. 8
Checked: 11 October 2026
Limitation: The magnet does not fall at exactly constant speed from the moment it is released; the ends of the pipe and other regimes are excluded.

Claim A05

How strongly the magnet is braked depends on the magnet, the geometry of the pipe, and the electrical properties of its material.

Electromagnetic braking: A simple quantitative model

Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics · September 2006 · DOI 10.1119/1.2203645

Evidence level: Level 2
Location: pp. 816–817, Eqs. 8 and 13, Table I
Checked: 11 October 2026
Limitation: The factors cannot be treated as independent of one another, and there is no supported “the more, the better” rule.

Magnet fall inside a conductive pipe: motion and the role of the pipe wall thickness

G. Donoso, C. L. Ladera, P. Martín; European Journal of Physics · 27 May 2009 · DOI 10.1088/0143-0807/30/4/018

Evidence level: Level 2
Location: pp. 862–865, §§4–5
Checked: 11 October 2026
Limitation: The factors cannot be treated as independent of one another, and there is no supported “the more, the better” rule.

Claim A06

During the steady fall, the model dissipates the lost gravitational potential energy through the pipe’s electrical resistance; the induced currents decay resistively.

Electromagnetic braking: A simple quantitative model

Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics · September 2006 · DOI 10.1119/1.2203645

Evidence level: Level 2
Location: p. 815, section II “Theory”, right-hand column; Eq. 1 and the paragraph on the decay of eddy currents
Checked: 11 October 2026
Limitation: No measured temperature rise is claimed; how large or noticeable it is remains open. The qualitative energy balance is not a new measurement.

Claim A07

Two independent research groups studied different aspects of the pipe experiment.

Electromagnetic braking: A simple quantitative model

Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics · September 2006 · DOI 10.1119/1.2203645

Evidence level: Level 2
Location: p. 815, authors and institution; pp. 816–817, experiment
Checked: 11 October 2026
Limitation: Earlier work cited in these papers does not count as additional independent measurements.

Magnet fall inside a conductive pipe: motion and the role of the pipe wall thickness

G. Donoso, C. L. Ladera, P. Martín; European Journal of Physics · 27 May 2009 · DOI 10.1088/0143-0807/30/4/018

Evidence level: Level 2
Location: p. 855, authors and institution; pp. 861–865, experiments
Checked: 11 October 2026
Limitation: Earlier work cited in these papers does not count as additional independent measurements.

Claim A08

Donoso et al. (2009) tested different wall thicknesses: the thicker-walled pipes they tested braked the magnet more strongly, but not according to a universal linear rule.

Magnet fall inside a conductive pipe: motion and the role of the pipe wall thickness

G. Donoso, C. L. Ladera, P. Martín; European Journal of Physics · 27 May 2009 · DOI 10.1088/0143-0807/30/4/018

Evidence level: Level 2
Location: p. 855, abstract; pp. 862–865, §§4–5, Figs. 4–7
Checked: 11 October 2026
Limitation: Applies only to the configurations studied; doubling the wall thickness should not be read as doubling the fall time in general.

Claim A09

Levin et al. compared one, two, and three stacked magnets; in their setup, the stack of two fell more slowly than both the single magnet and the stack of three.

Electromagnetic braking: A simple quantitative model

Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics · September 2006 · DOI 10.1119/1.2203645

Evidence level: Level 2
Location: p. 816, section III “The experiment”; p. 817, Table I and interpretation
Checked: 11 October 2026
Limitation: Not a universal rule and not our own measurement. Numbers from this study appear in the video only as attributed study data.

Source list

Q1
Yan Levin, Fernando L. da Silveira, Felipe B. Rizzato; American Journal of Physics (September 2006). Electromagnetic braking: A simple quantitative model. DOI 10.1119/1.2203645Checked 11 October 2026
Q2
G. Donoso, C. L. Ladera, P. Martín; European Journal of Physics (27 May 2009). Magnet fall inside a conductive pipe: motion and the role of the pipe wall thickness. DOI 10.1088/0143-0807/30/4/018Checked 11 October 2026
Q3
University of Iowa, Physics & Astronomy (Not stated; accessed 11 October 2026). Lenz’s Law – Tubes and Magnets. https://instructional-resources.physics.uiowa.edu/5k2025-lenzs-law-tubes-and-magnetsChecked 11 October 2026

How to read the evidence level: The level describes the kind of source for the claim in question, from Level 1 (the strongest kind, such as a systematic review, consensus report, official original data, original document, or court ruling) to Level 4 (secondary source). For scientific claims, Level 2 covers original studies with a suitable design and scientific textbooks. A level does not make a single finding certain; the limitation states what the source does not support. Only claims with a checked source appear on this sheet. How we check sources.

An unclear statement or an error? How we record corrections.