• Pixel-art sticker of Spinnor, personifying Angular Momentum, with the caption “Arms In, Spin Faster.”

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Spinnor

Angular Momentum Physics

\[I_1\omega_1 = I_2\omega_2\]
$4.99 USD
$4.99 USD
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Meet Spinnor, a spinning top who speeds up just by pulling his weights in. With no outside twist, angular momentum stays fixed, so cutting his moment of inertia from 3 to 1 kg·m² triples his spin. Collapsing stars become pulsars this way. Pixel-art kiss-cut sticker in 2, 3, 4 and 6 inches; equation, symbols and sources in the physics panel below.

Size
Surface

Flat $6 shipping worldwideMade to order, ships in 2–5 business days

Details

Size3″ × 3″

3″ × 3″ kiss-cut sticker.

Shipping

Flat $6 shipping on every order, worldwide, whatever's in it.

Delivery times & where we ship

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

Meet Spinnor, a spinning top who speeds up just by pulling his weights in.

A spinning object has angular momentum, its moment of inertia multiplied by its spin rate, L = Iω. The moment of inertia measures how far the mass sits from the axis. If nothing outside twists the object, its angular momentum cannot change.

So I₁ω₁ = I₂ω₂. If Spinnor starts with I = 3 kg·m² spinning once per second and pulls his weights in until I = 1 kg·m², he must spin three times per second.

His spin energy, ½Iω², goes up three times too. That extra energy comes from the work he does pulling the weights inward against their tendency to fly outward.

The same rule acts across the universe. When a star's core about the size of the Earth collapses into a neutron star about 20 km across, it can end up spinning hundreds of times a second. That is how pulsars get their amazing speed.

Equations

\[I_1\omega_1 = I_2\omega_2\]
SymbolMeaningUnit
\(I_1\) starting moment of inertia \(\mathrm{kg·m²}\)
\(\omega_1\) starting angular velocity \(\mathrm{rad/s}\)
\(I_2\) final moment of inertia \(\mathrm{kg·m²}\)
\(\omega_2\) final angular velocity \(\mathrm{rad/s}\)

Sources

  1. OpenStax University Physics Vol. 1 — Conservation of Angular Momentum
  2. Wikipedia — Pulsar

Field notes

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