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Current Affairs Sticker Sheet

Vortessa, Saltara, Pendulux & Libratrix | 9 Pixel Art s

\[\begin{gathered} f = \mathrm{St}\,\frac{U}{D}, \qquad \mathrm{St} \approx 0.2 \end{gathered}\]
$19.99 USD
$19.99 USD
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The Current Affairs sticker sheet gathers several Pixelated Physics characters on one page, each built on a real piece of physics. Nine kiss-cut pixel-art stickers on one A5 sheet: Vortessa (vortex street), Saltara (hydraulic jump), Pendulux (Foucault), Libratrix (L2), plus props. Peel them off one at a time and stick them wherever the physics belongs.

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Details

What you getA5 sheet · 9 stickers

One A5 kiss-cut sheet (5.83″ × 8.27″) on white sticker paper with 9 stickers, made to order.

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Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

Stickers about flow and motion: vortex shedding frequency, the depth ratio across a hydraulic jump, the Foucault pendulum's turning swing plane, and the Lagrange points where a small body can hold station.

Nine stickers on one sheet: four characters who make sense only while things are moving.

Vortessa’s line is Left. Right. Left. On the Beat. Flow past a cylinder sheds vortices from alternate sides in a staggered street of opposite spins, at a frequency f = St·U/D with the Strouhal number near 0.2 over a wide range of flows. Theodore von Kármán explained the pattern in 1911. That is the cylinder and its alternating swirls, St 0.2.

Saltara’s line is Fast and Shallow. Then Slow and Deep. When fast, shallow water (Froude number above 1) meets slower water downstream, it jumps abruptly to a deep, slow flow, and mass and momentum fix the depth ratio. You can see one in a kitchen sink, where the jet hits the basin. That is the step in the water marked JUMP.

Pendulux’s line is I’m Not Turning. The Planet Is. In 1851 Léon Foucault hung a pendulum in the Panthéon and its swing plane slowly turned against the floor, at the Earth’s rotation rate times the sine of the latitude. At the poles that is one turn per sidereal day; in Paris it takes about 32 hours. That is the rosette traced on the floor.

Libratrix’s line is Balanced. Barely. Nudge Me Often. The Sun–Earth L2 point sits about 1.5 million km beyond the Earth on the Sun–Earth line, where gravity and orbital motion balance. The balance is unstable, so spacecraft there, like JWST, fire thrusters now and then to stay. That is the Sun, the Earth and the marker at L2.

Equations

\[\begin{gathered} f = \mathrm{St}\,\frac{U}{D}, \qquad \mathrm{St} \approx 0.2 \end{gathered}\]
\[\begin{gathered} \mathrm{Fr} = \frac{v}{\sqrt{g h}} \\ \frac{h_2}{h_1} = \frac{1}{2}\left(\sqrt{1 + 8\,\mathrm{Fr}_1^2} - 1\right) \end{gathered}\]
\[\begin{gathered} \omega_{\text{prec}} = \Omega_\oplus \sin\varphi \end{gathered}\]
\[\begin{gathered} r_{L2} \approx R\left(\frac{M_2}{3M_1}\right)^{1/3} \end{gathered}\]
SymbolMeaningUnit
\(f\) shedding frequency: full left-right cycles per second \(\mathrm{Hz}\)
\(\mathrm{St}\) Strouhal number, about 0.2 to 0.21 for Re from about 300 to 200,000 (lower near onset) \(\mathrm{1}\)
\(U\) speed of the oncoming flow \(\mathrm{m/s}\)
\(D\) diameter of the cylinder \(\mathrm{m}\)
\(\mathrm{Fr}\) Froude number: flow speed over the speed of shallow-water waves \(\mathrm{1}\)
\(v\) depth-averaged flow speed \(\mathrm{m/s}\)
\(g\) gravitational acceleration \(\mathrm{m/s^2}\)
\(h\) depth of the flow \(\mathrm{m}\)
\(h_1, h_2\) depths just before and just after a planar jump in a straight channel \(\mathrm{m}\)
\(\mathrm{Fr}_1\) Froude number of the incoming flow \(\mathrm{1}\)
\(\omega_{\text{prec}}\) rate at which the swing plane turns relative to the floor (clockwise seen from above in the Northern Hemisphere) \(\mathrm{°/h}\)
\(\Omega_\oplus\) Earth's rotation rate relative to the stars: one turn per sidereal day of 23.93 h \(\mathrm{°/h}\)
\(\varphi\) latitude \(\mathrm{°}\)
\(r_{L2}\) distance from the smaller body to L2 (second line: Sun–Earth L2, beyond Earth) \(\mathrm{m}\)
\(R\) distance between the two bodies \(\mathrm{m}\)
\(M_1, M_2\) masses of the larger and the smaller body \(\mathrm{kg}\)

Sources

  1. von Kármán (1911) Ueber den Mechanismus des Widerstandes, den ein bewegter Körper in einer Flüssigkeit erfährt, Nachr. Ges. Wiss. Göttingen, Math.-Phys. Kl., 509–517 (EuDML)
  2. Strouhal (1878) Ueber eine besondere Art der Tonerregung, Ann. Phys. 241, 216
  3. Chanson (2009) Development of the Bélanger Equation and Backwater Equation by Jean-Baptiste Bélanger (1828), J. Hydraul. Eng. 135(3), 159–163
  4. Watson (1964) The radial spread of a liquid jet over a horizontal plane, J. Fluid Mech. 20, 481
  5. Foucault (1851) Démonstration physique du mouvement de rotation de la Terre au moyen du pendule, C. R. Acad. Sci. 32, 135–138 (Wikisource)
  6. APS News (2007) February 3, 1851: Léon Foucault Demonstrates That Earth Rotates
  7. Encyclopaedia Britannica — Lagrange point (Lagrange 1772; L4/L5 stability above 24.96; Trojan asteroids)
  8. Routh (1874–75) On Laplace’s Three Particles, with a Supplement on the Stability of Steady Motion, Proc. London Math. Soc. s1-6, 86–97

Source Strouhal, V. (1878). Ueber eine besondere Art der Tonerregung. Annalen der Physik 241, 216–251.doi.org/10.1002/andp.18782411005

Field notes

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