its 8:30 in the morning and we're very excited
because today we're getting a special behind-the-scenes look Suzanne Shaw
and Matt Evers
the 2008 winners of ITV's Dancing on Ice
as they're practicing behind me for the next season. I've gotta say
my most favorite outdoor ice rink I've ever been on
It's brilliant! I'm having so much fun and it's been great to
be able to use the space which is very similar to the studio rink
of dancing on ice so it really helps us. I grew up skating on an outdoor ice rink
which is where I started so to be back on an outdoor rink has kinda come
full circle for me
so it's it's been amazing
I don't know about you, but I'm absolutely awful at ice skating
Everyone here in At Bristol has been getting a little bit better over the weeks
we've had the ice rink
but we're certainly nowhere near as good as Suzanne and Matt
and we can't pull off the same kinds of tricks and spins that they're able to do
so to help us understand just how they do those spins
we're going to investigate the physics of Dancing on Ice
the question we're going to ask today is how does an ice skater manage to spin so fast?
Start off with everything open, your arms out and leg out and then
as soon as you want to speed up, bring everything in, and then you bring everything in
you go really fast
To understand how these figures skaters are able to pull off these
kinds of spins
we need to take a look at the forces these skaters are under.
This is Jazz, our model figure skater
demonstrating the moment of inertia which is the property that tells us how
easy it is for something to rotate
as defined by the equation: moment of inertia
equals mass multiplied by the radius squared
But what does that mean? well as Jazz spins
the length of her outstretched arms is the radius , or R
The mass is M. With her arms wide
the bigger radius results been a bigger moment of inertia
so it's harder to rotate. As she draws her arms in
the radius gets smaller reducing the moment of inertia
so it becomes easier to rotate.
But why does she spin faster?
To help us understand this i'm with Nerys of the live science team
So Nerys, why does Jazz speed-up? Well, it's all to do with the conservation of
angular momentum
and what does that mean? Well Jazz has angular momentum because she
spinning and that's the moment of inertia multiplied by
the angular velocity, how fast she's spinning. So where does the conservation part come in?
If there are no external forces acting on her, then angular momentum is conserved,
it stays the same. When she pulls her arms in, she reducing her moment of Inertia, so
something else has to change to balance that out.
so the angular velocity increases? well that's the theory let's try it out
I'm going to get you to hit the ball around a pole and we'll see what happens.
So, as the ball rotates around the pole, the string gets shorter,
reducing the radius, giving us a smaller moment of Inertia. And because the angular momentum can't
change the ball speeds up to balance out. That's right
just like what happens with our ice skater.
With a bit of skill and a lot of practice
these figure skaters are able to use the conservation of angular momentum
and the physics of Dancing on Ice to achieve those fast spins
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All that's left for me to do is put it into practice.