Hello and welcome.
Today we're going to talk about air pressure and that classic physics demonstration,
the soda can crush.
What I have here is an empty, open soda can. I'll show you this one.
The soda's been consumed, the can is open, and it's empty on a hot plate heating up with
about 5-10 mL of water.
Now the water is boiling in the bottom of the can and the steam, which may be visible,
is coming out through the top of the can.
In this demonstration, the can is picked up and put upside down into a bath of ice water,
which I have here.
I'll put on my safety goggles.
I'll grasp the can firmly at the bottom with my palm facing up, and I'll get ready to upend
it in the ice water.
One, two, three.
Just like that, the can is crushed.
We can see that it's been quite well demolished. Very well crushed.
While vivid and certainly one of the students' favorites as a demonstration,
this is entirely qualitative.
We can see the can is crushed. We can see the new shape.
We heard the can crush, but we weren't really able to take any measurements.
What I propose to do is to do the same classic demonstration -- empty, open soda can with
about 5-10 mL heating on the hot plate.
In the meanwhile, I'll set up a data collection experiment here with my Absolute Pressure
& Temperature Sensor, my data collection system, and my data collection software.
I have everything connected to the computer
and I'm ready to collect absolute pressure and temperature data.
A little bit more about my setup here. Connected to the Absolute Pressure & Temperature Sensor,
I have this length of long, hollow tubing.
It's probably nearly a meter long, and out at the end I have connected my Fast Response
Temperature Sensor, which you can see right here.
Now I've connected it just by twisting around these little twist ties, the kind you get
on bread wrappers.
That keeps it connected to the end of the tubing.
What I'm going to do is introduce it down into the can just before I put the can
upside down into the water.
Alright. I'll go ahead and begin recording pressure and temperature data and we can see
that we're at regular atmospheric pressure here, about 101 kPa.
Just like before, I'll go ahead and grab the can with the tongs down at the bottom,
and I'll introduce the tube with the temperature sensor
about two-thirds of the way down into the can.
We can see, of course, that the temperature is increasing because it's down there
near some boiling water.
Here we go, into the water. One, two, three...
...and crush.
Now I'll stop recording my data, and we'll go ahead and scale the graph so we can see
exactly what happened here.
I'll close the tool palette.
Although I have several data points to the left between 0 and 30 seconds, at 30 seconds
thereabouts is where the action seems to have occurred.
From this point, of course, I can go ahead and analyze my data.
I can begin by dragging the axis either to the left or to the right.
I can translate the entire graph to the left, which I'll do, so that I can stretch the x-axis
just enough to give myself an idea of how much time it took for that phenomenon to occur.
You'll notice that my sampling rate is fairly high.
I've been measuring data at the rate of 100 Hz.
I think you can see that because this phenomenon happened so rapidly,
that rapid sampling rate is very advantageous.
There I have a little bit better look at the moment of crush, and I also see what happened
to the temperature.
There we have it. An example of a qualitative can crush demonstration,
and then a very easily adapted quantitative, measurement-based can crush demonstration.