Hi, I'm Mrs. Charles with I Spy Science and Wired for Science at the Cary Area Library.
Today I want to show you two science demonstrations that you can
experiment with and do at home. Both use water. The first is called Bending Water
and the second is called Defying Gravity. I hope you have fun doing both.
The materials you need for Bending Water are a balloon, a comb-- maybe try a variety
of combs-- a clean head of hair and a sink with water. To do this experiment
the first thing I'm gonna do is the balloon. You prime it first, blow it up,
and tie it and now I'm going to use one that I've already done. So, you take this
balloon and you're gonna rub it against your hair like this. Then you're gonna
turn the water on-- just a tiny stream-- and then you're gonna put the balloon like this and watch it bend.
Wow, that really worked well!
Now I'm going to try the experiment using a comb.
I have short hair so I'm predicting it might not work as well as the balloon did but we'll see.
So, I'm gonna comb my hair, run it through at least 10 times through your hair.
I think if I had longer hair it might work better. Okay, I've done it enough so
hopefully there's some static electricity there.
I can see it's moving the bottom portion of the water but it's not moving very much.
When I did it one other time it did work. I would try someone who had long hair over short hair.
So, why does the water bend? The balloon rubbing on your hair and the
comb running through your hair cause the tiny parts of the atoms in your hair
called electrons to collect on the balloon and the comb. The balloon and the
comb pick up a charge of static electricity. The electrons have a
negative charge. Now, negative charges are attracted to a positive charge.
So, both the balloon and the comb are attracted to the water which has a
positive charge. The attraction is strong enough to actually bend the water.
The materials you're going to need to do Defying Gravity are a large needle or a
safety pin-- I'm using a safety pin-- a pencil, scissors,
either-- I have three kinds of cups-- you can use whatever you'd like.
I've got paper, plastic, or foam, string and water from a sink.
The first thing you need to do is ask an adult to help you make the two holes opposite
opposite of each other near the top of the cup with your safety pin.
I'm taking my safety pin and poking it in, first of all I'm using two foam cups
because when I did one it didn't work very well and it broke. So I poke in a
hole on one side, I take the pencil and carefully push it in so I have a big
enough hole to be able to put my string through. Then on the opposite side, I'll
turn the cup around and I'll make another hole right at the bottom of
the rim of the second cup, then I push my pencil in. There, now I have holes
opposite of each other through both cups. That will make it sturdy enough to hold
the water. The second thing I do is take a piece of string, estimate about three
feet-- you don't have to measure-- and cut the string.
Now, I'm gonna take one end of the string, poke it through the hole of the cup.
You needed the hole big enough to be able to use, to get the string in. You could use
yarn but string is easier and smaller to fit through the hole. So, I tied it once
then I'm gonna make a circle. Take the short end and pull it through. That makes
a knot on one side of the cup. Now I'm going to take the end of, the other end
of the string, and put it through the hole on the other side of the cup.
Make a circle, like this: put the short end through the hole and pull it tight,
then make another circle. Put the short end through the hole and pull it.
That's making a knot on the second side. Now you have a handle with a cup.
The next thing you're gonna do is fill the cup halfway with water.
So, how does this work?
Gravity would allow the water to fall out of the cup if you turned it upside down but as
you spin the cup around you might feel that it wants to fly off in a straight
line from you. You might even like to accidentally let go of it and see if
that happens at home. This is a demonstration of Newton's
First Law of Motion, inertia, that an object will continue in a straight line
unless an outside force, in this case, the string and your arm will act on it.
So, both the cup and the water move in a circular motion and the water stays in the cup.
Okay, so we're ready for the fun part of this experiment.
You have your cup, you're holding it by the handle, you're gonna be outside because it's
summer and it's great to do outside-- you don't want to get inside wet.
You're going to swing it around in a circle away from anybody else-- you don't
want to hit anybody. So, here we go. Hopefully the water will stay in the cup.
And it's working! There's hardly any water coming out.
Okay, I'd like you to experiment at home. Try different kinds of cups. Here's a plastic
one, here's one that's not even a cup. Do they all work the same? Try adding more
or less water to your cup. Do you have the same success? Try whirling it faster
or slower. Does the water stay in the cup? Try using a bucket. Does that work the same?
Good luck doing both of these experiments. I'll have more
demonstrations next month for you to do at home and experiment with while we
don't have our usual I Spy Science and Wired for Science programming at our
Cary Area Library. Have fun and hopefully we'll see you at our usual classes soon.
Thanks for watching.