In a perfect world if this were a rubber ball,
and I dropped it down to the floor, it would bounce up to the same height, if it was completely elastic.
But it would go, in practice, to a lower height, and then a lower height, and then a lower height...
This object apparently is called a dropper popper.
It has a little rod at the top and it has some rubber that comes down this way,
only you can bend it the other way.
And it has two states which are quite stable: that state
and that state.
And what I'm going to do is put it into this state,
and drop it on the floor,
giving it a spin so that it remains in the horizontal plane.
And if I do this and drop it... are you filming it now Brady?
...it bounces up. And I can catch it -- even an old man like me.
And if I drop it from this height...
...it goes up higher than the height from which it was dropped.
This, at first, made me addicted to it because I couldn't work out...
...why it was doing this, because it seemed extremely strange
that you would be able to drop this... and catch it and it goes up higher than before.
And I also learned that I could do it with both hands.
And I've been trying to do it with both hands and catch it, but it's impossible.
[Brady] Orr, almost!
[Professor Bowley] On the rebound!
When it's at this height we say it has energy because I've done work lifting it up to this height.
So there is an energy due to its position,
and if I drop it on the floor, if it bounced elastically it would come up to the same height.
The thing which is surprising is that it goes further.
What happens is you deform this... you have to really push hard on this to get it to go into that state...
It requires quite a bit of work to get it into that state,
and it always... if I tip it back... it will go back automatically into that state.
So you started off in this state, which has cost you a bit of work because you have to force yourself to do it...
Now, when it drops down, and it hits the floor,
it can go into the other state, if it whacks down hard enough.
So if I were to do this from a very low height, nothing happens.
If I drop it from this height...
...then it bounces much higher.
When it lands it hits the floor,
suddenly, the central pillar comes out, hits the floor, and pushes up,
and it jumps in the air.
This is releasing energy because this state requires you to do work...
that state has a lower energy -- lower potential energy -- and that energy is released
by pushing on the floor and raising up higher.
To change it to the other configuration I had to pull on this rubber
and extend the molecules of the rubber and do work on it.
And if I do that and get it to a certain point it will click over.
And now I've stretched these rubber molecules a little bit,
it's much more taut -- you can feel that it doesn't move so much.
When it hits the ground, the top of this dome...
suddenly gets inverted and becomes a dome pointing the other way,
and that pushes this rod down, and then it hits the floor and bounces up.
When you have any object like this and you spin it
the angular momentum of the spin remains constant and keeps the axis about which it rotates vertical.
And that's what I'm trying to do. [Brady] Like a top? [Professor Bowley] Like a spinning top,
so that when it hits the floor I'm hoping that I haven't twisted it sideways by any little bit,
and therefore when it falls down it's likely to release the maximum amount of energy
because it's hitting and somehow on all faces at the same time and coming up.
If I had it coming down a hitting on the side...
well, you can see that can still work, but it just flew out of my hand in one way.