Rotational Physics and the Conservation of Angular Momentum

If there’s one topic that really makes physics feel like magic, it’s rotational motion. The idea that a spinning skater can speed up just by pulling in their arms never fails to grab attention. But behind the spectacle is a principle every student needs to understand: the conservation of angular momentum.

And what better way to teach it than with a hands-on PASCO experiment?

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The Setup – Physics in Action

We use:

• A PASCO rotational motion sensor

• A Newton force sensor

• A string with a small mass attached

The student swings the mass in a horizontal circle above their head, the string passing through the force sensor. The sensor records the tension in the string – the inward centripetal force keeping the mass moving in a circle.

The rotational sensor, meanwhile, records the angular speed of the system.

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What Students Discover

1. Centripetal Force: The faster the mass goes, the greater the tension measured by the force sensor. Students can see the mathematical link:
   $F = \frac{mv^2}{r}$

2. Changing the Radius: Shortening the string (pulling the mass closer in) makes the angular velocity increase. This isn’t just “because it looks cool” – it’s conservation of angular momentum in action.

   $L = I \omega$

   Where $L$ is angular momentum, $I$ is the moment of inertia, and $\omega$ is angular velocity. Decrease $I$, and $\omega$ must increase to keep $L$ constant.

3. Real-World Connections: From ice skaters to planets, the same principle applies. Students can immediately see how the laws they’ve measured with sensors scale up to explain cosmic phenomena.

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Why This Works as a Lesson

The combination of hands-on experience and digital sensors bridges the gap between theory and reality. Instead of memorising equations, students watch the numbers change in real time, linking the physics to something they can feel in their own arms.

And let’s be honest – swinging a mass around your head is a lot more memorable than staring at a textbook diagram.

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✅ With PASCO’s sensors, rotational physics goes from abstract to concrete. Students don’t just learn about angular momentum – they see it, measure it, and never forget it.