At this time, we present a special
transmission for schools.
One in an experimental series designed to test
techniques and materials in the supplementary use of
television as a teaching aid in the elementary grades.
[ Background Sounds ]
Boys and girls, have you ever pretended a piece
of wood was a boat?
What happens when you throw the wood into water?
It floats, doesn't it?
Now, here's a metal screw.
What will happen if we throw the screw into the water?
Will it float?
Of course not, the screw sinks.
Why? Why does the screw sink while the wood floats?
Well, that's the question we'll think about today
in your science program, Young Experimeters,
a science lesson for the upper grades in the
Wisconsin School of the Air.
Your teacher is Lloyd Litke of Wisconsin State
College at Whitewater, and here's Mr.
Litke. Hello, boys and girls,
hello, young expometers.
Say, have you ever sailed a boat on a cake pan lake
or aquarium reservoir?
No? Then supposing you sail one with me this afternoon.
Let's sail a stern wheeler like this.
You know, a stern wheeler is a boat that has the power
source here at the back.
A great big paddle wheel.
Let's turn by an engine.
And the engine is powered by steam, by coal, by oil.
Now, we can't do that with our engine, with our boat.
So, let's try this paddle wheel.
Let's wind our boat, our put power into it.
Let's put the power of our muscles into twisting this
paddle wheel around and around.
Here it goes.
Can you see me twisting the paddle here?
Looks like we've got enough power.
So now, let's put it down here on cake pan lake like this.
Let go of the paddle wheel, and there she goes.
Now, maybe you didn't see enough of this, boys and girls.
Let's try it again.
Only this time, let me wind the rubber band,
the opposite direction.
That's around this way.
In the opposite direction to the way we did it the first time.
We twisted around and around to get some power stored
up in the rubber band to turn that paddle wheel.
Oh, I guess that's enough.
Now, boys and girls, where will I put this boat?
Shall I put it here?
Or would you suggest I put it over at this
end of cake pan lake?
You say over here?
Alright, let's try it.
I'll let loose of the paddle wheel, and sure her not.
We wind it up in the opposite direction,
and it goes backwards.
So we can run our boats either forwards or backwards.
Let's put the boat boys and girls.
That even though the power has been used up, the
boat is still floating.
Why boys and girls?
Do some things float and others don't.
Remember how that heavy metal piece sank to the bottom?
Let's put that up on the blackboard.
Why? Float.
Why do boats float?
Why do some things float and others don't?
I'm going to take this cake pan lake out of here,
and let's start our experimenting by
weighing things.
We'll weigh them on this homemade balance or scales.
It looks like a teeter totter, doesn't it?
Remember how you used a teeter totter when you
were little boys and girls?
Remember how much fun it was when you could teeter
totter with somebody about your own size?
How easy it was to make the teeter totter go up
and down because your weights were about the same?
Now let's make this a teeter totter.
If I put a penny over in this pan, the balance goes down.
Now to bring it back into balance, I put a
penny over in this side, and notice that the arm
here goes back and forth, bounces up and down,
just like you used to bounce up and down when you teeter totter.
And then stops in a horizontal position.
In other words, whenever we find the weights on either side,
the board will be parallel to the earth like this.
I put another penny over on this side, and of course,
down again goes that arm.
I put a penny over here, and it bounces up and down again,
and then stops in a horizontal position.
So we know that whenever we have this arm in this fashion,
the things on either side must weigh the same.
Oh look here.
Here we have a sinker.
I think I ought to put some, can you see it all right?
This is a big sinker.
This is the kind they use when they go fishing
for catfish and carp.
So it'll carry the line way down to the bottom
of the river or the lake.
Could I weigh this sinker with my teeter totter or my balance?
I put the sinker over there, and in the other pan,
I'll keep adding pennies.
One, two, three, four, still not enough.
Five, six, seven, eight, nine.
Looks like it's going away just a little bit more.
We'll take one penny out.
Got this thing back here where it belongs.
We find that our sinker must weigh a little bit
more than nine pennies.
So let's see if we can weigh this stern wheeler boat.
I think we could do that.
Be kind of hard to put it up here, wouldn't it?
Might I suggest that we try weighing this boat this way?
It's touching the box.
I guess I'll have to get some books and raise my
balance a little higher.
First of all, we notice that it weighs less than the sinker.
So let me take all the pennies out, and we'll add
some over here to see how much that boat really weighs.
One, two, three, four, five, six, seven.
It weighs a little bit more than six pennies.
So the weight of the boat is about equal to six pennies.
Now, you believe that, don't you?
Let's just check.
Remember our sinker weighed about nine pennies.
So I'll put a string on my sinker like this,
tie it and we'll replace the boat with the
sinker here, like this.
We won't make it too short here.
Well, that ought to do it.
We've got the pennies out so we can again make sure here.
One, two, three, four, five, six, seven, eight, nine.
It doesn't make much difference whether we put
our weight on top of the arm here or at the bottom.
So we can say that we have a sinker that weighs
more than the boat.
But remember that boat floated.
Now, do you suppose, boys and girls, that the water that
this boat is floating in actually pushes up on the boat?
I wonder then would the same thing happen if we put
our sinker in the water?
Let's try it.
Here I've got a glass of water.
I'm going to put it over here.
Now notice our scales is pretty nearly balanced.
Now I'll put my sinker down into the water, make sure that
it doesn't touch the water.
Now wait a minute.
What seems to be happening here, boys and girls?
It looks like the sinker has lost some weight.
How much weight do you think this sinker has lost?
Or I guess we can't say it's lost but it seems to have lost.
Oh, we'll take out some pennies here.
See if we...
That bounces up and down.
Looks like it's pretty nearly balanced from here.
It may be just a little heavy on this side yet.
But it looks like that sinker was pushed up by
a force about equal to the weight of the penny.
So you see boys and girls, all things are being pushed
up somewhat by the water.
Now Archimedes said this.
He said an object in a fluid is pushed up by a
force equal to the weight of the water it displaces.
I suppose you and I'd say pushes aside.
And here we have an object, the sinker, in some water.
And it was pushed up by a force equal to how much?
Equal to the weight of one penny.
Now, still we have another problem here.
He said, "Boys up by a force equal to the weight
of the water it displaces."
How can we find out how much water an object displaces?
Let me give you a hint.
Archimedes found the answer out to that by taking a bath.
Yeah, a bath.
Let's you and I think for a minute boys and girls
about taking a bath.
Let's say that we filled our bathtub about
half full of water.
Now we're going to jump into the bathtub.
What happens to the water level?
Well sure, it rises, doesn't it?
Well now let's see if we can compare the amount of
water displaced by our sinker and the water
displaced by our boat.
We'll turn the glass around here boys and girls.
Can you see this piece of adhesive tape?
I have it right here so it's even with the top
surface of the water.
Then I'll take my sinker again.
Now I want you to watch the water level if you possibly can.
I put my sinker down in there and why it must displace only
a very small amount of water.
I can't see any water above the level of the adhesive tape.
Now let's try the same thing with our boat.
We put our boat.
Can you see the water rising here?
We put the boat way down in.
Just look at the amount of water that boat displaces.
Now remember we had a weight that weighed a little
bit more than the boat.
We have a boat that displaces a great deal more water.
Let's come back over here and see if we can put down
a couple of words here that will help us answer that.
Why boats flow?
First word is weight.
The sinker weighed more than the boat.
Second word is volume.
The boat displaced a lot more water than the sinker did.
So boys and girls let's come back to this problem.
Here's the battleship Wisconsin weighing thousands
of tons and yet it floats.
And here's a little nail like we have in our teeter totter here.
And it sinks.
Why? Well the battleship Wisconsin
floats because it displaces large amounts of water.
So much water that the water displaced weighs
more than the boat.
So the nail is heavy and displaces just a
little bit of water.
Boys and girls why do boats float?
Boats float because they weigh less than the water
that they push aside.
Now young experimenters it's your turn.
Time for you to try out the paddle wheel experiment
you saw on the program.
And to experiment with the other idea suggested in
your instruction sheet.
Remember to keep a record of your observations
and send it to us, care of WHO-TV in Madison.
Your teacher on these test programs of young
experimenters has been Lloyd Litke of Wisconsin
State College at Whitewater.
Next week at this time we'll see a Nature Study program with
your radio friend Ranger Mac.
This is the Wisconsin School of the Air.
The preceding program was a special
transmission for schools, one in a series of
experimental programs on which research is being conducted
to test the effectiveness of utilizing television as a
supplementary teaching aid.
[]