Hello and welcome. My name is Elizabeth Kennedy.
We're here today to do a demonstration -- a classic physics demonstration --
of getting a hard-boiled egg into a bottle that it looks like it can't possibly fit into.
And not only getting it into the bottle,
but getting it in without breaking or destroying the egg.
What I have here is just a regular, old-fashioned milk bottle.
You can see that the opening of the milk bottle is smaller than the egg.
How we're going to do this -- how this is usually done --
is to take some means of lighting a fire,
and putting, in this case, a lit wood splint into the bottle.
I'll go ahead and do that, but before I do,
let me just make sure that I am following safe science.
I'll put on my safety goggles, and I havea little beaker of water to put my spent match into.
So I'll light this splint.
Alright. I'll set this down into the bottle, put the egg on top, and just see what happens.
Sure enough, in it goes.
It's a fairly shocking and fun event for students to see who have never seen it before,
which I suspect is why it's such a classic.
Very clever demonstrators can then again get the egg back out of the bottle,
but more about that later.
One of the things that we're also going to talk about is how to take these fairly qualitative event,
with the smell and the sound and just seeing what happened,
and turn it into a bit more of a quantitative experiment.
The way we're going to do this is we're going to take another bottle that's been adapted
-- this is the PASCO Metabolism Chamber -- to accept the pressure sensor.
Let me show you what we've got here. We have a Dual Pressure Sensor.
We're going to connect to that a stopper that will fit into this hole in the side here,
and the other end be connected to the pressure sensor, like this.
In my PASCO Metabolism Chamber, which has a hole in the side,
I have a birthday candle that's been melted onto a penny.
That's just so I can drop it in a top or place it in through the hole and it stands upright.
I can place it right in the center so that I can easily then light it.
Now you'll notice that the diameter of the openings is not exactly the same.
This is obviously a smaller opening. Nevertheless, we're going to try this.
I'll get another egg out of my container here.
By the way, I've got my eggs a little bit moist.
It helps to have them just a slight bit lubricated.
I'm going to begin my experiment, but not before I started to collect some data.
What I have here is a graph display.
This is for the pressure inside the bottle.
Then the second port will be just measuring normal atmospheric pressure
while this all takes place.
I'll begin with my pressure data recording.
I'll go ahead and light the candle inside the metabolism chamber.
Now, very carefully, I will insert the rubber stopper into this hole in the side.
Place the egg on top.
And I'll just hold it in place. I'm not actually pressing with my finger.
I'm just holding it in place until I know a seal has been formed.
We'll just see what happens.
As I had mentioned, the difference in the diameter between the two openings makes it
look like this egg is really going to have to squeeze tightly to get in there.
But you still should be able to see that it's trying. It's really trying to get in there.
If I had smaller eggs available, that might be an easier task for the egg.
Meanwhile, let's think about what's going on while we watch and see what happens to
this egg, compared to this one.
We have a pressure measurement being taken inside the bottle, inside the metabolism chamber,
as well as a pressure measurement being taken in atmospheric pressure.
As we can see from the graph, atmospheric pressure is about 100.8 kPa.
Meanwhile, inside the bottle, it's about 92.2 or 92.3 kPa.
So it's quite a bit lower pressure inside the bottle.
Well, difference in pressure is difference in forces.
What this means is that the top of the egg on the outside of the bottle is experiencing
a greater force over its surface area.
Of course, force divided by an area is pressure.
Inside the bottle, there is a smaller force, less pressure, lower force per surface area.
If there is a difference in pressure, then there is a difference in forces.
The imbalanced force is what eventually causes the egg to get forced into the bottle.
In this case, trying to be forced into the bottle, but having a difficult time of it.
What we can see from our pressure graphs is that the pressure inside the bottle has dropped
to a value and is holding steady there.
It's not continuing to decrease,
so I doubt that this egg will make it all the way into the bottle.
We can at least get a look at the difference between the pressure and therefore the force
on the egg out here and the force on the egg inside.
As I mentioned earlier, some demonstrators can actually get the egg back out of the bottle.
Although this egg has sustained a little bitof damage from its trip into the bottle,
I think that I can probably get it back out of the bottle.
It still doesn't want to come back out. It still clearly doesn't fit.
But what I've propose to do is to take a can of compressed air
and with the little straw tube on it, press that up in, beyond the egg.
We'll see.
It may not work this way. I may have to change the orientation of the egg.
It looks like the wide end of the egg is facing down, so I'll try to get that changed.
I'll try this again.
There it is -- a little bit messier than I'd like -- but the egg's back out.
Thank you very much for joining us today. I have some cleanup to do.
I hope you've enjoyed seeing this classic physics experiment that's normally qualitative,
be a bit more quantitative.
Thank you.