Ice skaters use a cool science idea called the conservation of momentum to spin faster when they skate.

Here’s how it works:

When a skater pulls their arms and legs closer to their body, they can spin faster. This happens because they change something called their moment of inertia, which is a way to describe how much mass is spread out from the center of their spinning.

1. Initial Moment of Inertia (I₀): When a skater has their arms out, their moment of inertia is bigger. It can be thought of like this:

   • I₀ = mass of arms * distance of arms squared + mass of legs * distance of legs squared.

2. Final Moment of Inertia (I_f): When they pull their arms and legs in, their moment of inertia gets smaller. It looks like this:

   • I_f = mass of arms * smaller distance squared + mass of legs * smaller distance squared.

Now, let’s talk about the conservation of angular momentum. It means that the total amount of spinning motion stays the same. In simple terms:

• Before they start spinning, we have: L₀ = L_f (the amount of motion before equals the amount after).
• This translates to: Initial Moment of Inertia times Initial Spin Speed = Final Moment of Inertia times Final Spin Speed.

When the skater makes their moment of inertia (I) smaller by pulling in their arms and legs, their spin speed (ω) has to get bigger.

In practice, this means a skater can spin 3 to 5 times faster just by using this technique!

This shows just how important the idea of momentum conservation is in sports like ice skating.