Balancing a Yardstick

Balancing a Yardstick

Here's an interesting experiment that involves gravity and balance!Hold a yardstick on your index fingers (i.e. the first finger on each hand) with your arms spread wide apart.
What will happen if you move your right hand towards your left hand? At what point will the yardstick fall?Try it! Only move your right hand (try not to move your left hand), and slowly slide your right index finger along the yardstick until it reaches your left hand. The yardstick will keep shifting so that it remains balanced!

Tying a Knot

Tying a Knot

Can you tie a knot in a string without letting go of the string?Hand someone the ends of a string as in the picture, and challenge him to tie a knot in the string without letting go of the string. He can't do it!
Here's the secret!Fold your arms, and then grab one end of the string in each hand.
Slowly unfold your arms.You tied a knot without letting go of the string!

Spinning Illusion

Spinning Illusion

Here is an interesting optical illusion that you can make!Fold an index card (or a small piece of heavy paper) in half both ways. With a heavy marker, draw 4 lines starting at the top center of the index card, as shown in the picture.
Carefully poke a thumb tack through the center of the index card from the bottom.What will you see if you spin the index card on the thumb tack? Try it and see! Somehow the straight lines turn into a circle within a circle when you spin the card!

Can You Pick Up an Ice Cube without Touching It with Your Fingers?

Can You Pick Up an Ice Cube without Touching It with Your Fingers?

Place an ice cube into a cup of water.
Lay a piece of cotton string or yarn across the ice cube.Then sprinkle some salt onto the string.
Wait a few moments, then lift up the string with the ice cube attached to it!Salt lowers the melting temperature of ice, so the ice melts around the string, then it re-freezes around the string.

Knock Out a Coin

Knock Out a Coin

Here's an interesting physics experiment!Stack up some coins on a table, then put your finger on another coin. Now push your coin towards the stack and let go of it so that it slides and hits the stack.
If you slide your coin into the stack with enough force, it will knock the bottom coin out without knocking over the rest of the stack!

Can You Drop a Card onto a Piece of Paper?

Can You Drop a Card onto a Piece of Paper?

Place a piece of paper on the floor, then try to drop a playing card onto the paper.
It's not easy to do!
Hold the card like this, and ask someone if he can drop the card onto the paper.Don't tell him how to hold the card, just let him assume that he is supposed to hold it this way!
When he can't do it, you will be able to do it because you know the trick!The trick is to hold the card as flat as possible, as in this picture. Give it a try!

Can You Catch Two Dice in a Cup?

Can You Catch Two Dice in a Cup?

Hold a small plastic cup, and place two dice between the cup and your thumb.
Lift the cup up into the air and release one of the dice.
Can you catch the die in the cup?Now comes the tricky part! Can you lift the cup up into the air and release the other die and catch it so that both dice are in the cup?

Can You Balance an Egg?

Can You Balance an Egg?

Hold a hard-boiled egg carefully on one end and try to balance it.Ask someone if he can make it stand up on its end. Let him try a few times, but he can't do it!
Here's the secret!Hold the egg so that the narrow end is pointing up. Now hit the egg onto the table hard enough to break the shell. Now it is standing on one end!

Comb Kazoo

Comb Kazoo

Here's an experiment with sound.To make a kazoo, get a small plastic comb and tear off a piece of waxed paper which is just big enough to be folded over the comb.
Fold the waxed paper over the top of the comb, then hold the comb against your mouth with your lips open.Make a loud "HUMMMM" sound, and you should hear the kazoo noise as the waxed paper vibrates. Don't just blow onto the comb, it's important to use your vocal cords and make a humming sound. When you get the hang of it then you can make music on your new instrument by humming different tunes!

Can You Catch Coins Off of Your Elbow?

Can You Catch Coins Off of Your Elbow?

Here's a tricky experiment with gravity!First, balance one or more coins in a stack on your elbow.
Then straighten your arm and try to catch the coins!

Mobius Strip

Mobius Strip

Carefully cut out a strip of paper.Then cut two more strips.
Make a circle with one of the strips, then tape the ends together.
On the outside of the circular strip of paper, draw a red line in the middle all the way around the circle (or use some other color).Notice that the circular strip has two sides. It has an "outside" (with a line drawn around it) and an "inside" (with no line drawn on it). Draw a black line all the way around the circle near one edge. Notice that the circular strip has two edges (one with a black line near it, and one with no black line near it).
Carefully cut all the way around the middle of the circular strip (where the red line is in the pictures).Notice that you end up with two circular strips.
With another strip of paper, make a circle again but don't tape it yet.Imagine that one end of the paper has an X on the outside. Twist that end over so that the imaginary X is facing downwards, then tape it to the other end.
Now you have a circular strip with a twist in it.This is called a "Mobius Strip."
Draw a red line in the middle all the way around the Mobius Strip (or use some other color), just like you did with the circular strip.Notice that the Mobius Strip only has one side! It doesn't have an "inside" and an "outside" like the circular strip does! How is that possible? If you draw a black line all the way around the Mobius Strip near one edge, you'll see that the Mobius Strip only has one edge! How is that possible?
Carefully cut all the way around the middle of the Mobius Strip (along the red line in the picture), just like you did with the circular strip.Notice that it makes one large twisted circular strip instead of two circular strips!
With the third strip of paper that you cut out in step 1, make another Mobius Strip.This time, cut all the way around the Mobius Strip near the edge (where the black line is in the pictures above). Notice that this time you end up with two linked loops! Weird!

Straw Rocket

Straw Rocket

Here's a fun thing that we recently invented!Take the paper strip from step 1 of the Flexagons (above), or cut out a new strip of paper about 2 1/2 inches high and 8 1/2 inches wide. Roll the paper around a straw, but not too tightly.
Flatten one end of your paper tube, then fold a piece of tape over it.Slide the paper tube onto the straw, then blow your Straw Rocket across the room! Make sure that you won't hit any people or any breakable objects!
Notice that the Straw Rocket flies a short way and then starts to tumble in the air.To fix this, cut out 3 small triangles.
Carefully tape the small triangles to the end of your Straw Rocket near where the straw slides into it.Now your Straw Rocket will fly a lot farther and straighter! When you see pictures of real missiles and rockets, now you know why they have those fins on them! Try some experiments: Does a shorter Straw Rocket fly better than a longer one? Does it make a difference if you have only 1 or 2 fins, or if you have more than 3 fins? Who can shoot their Straw Rocket the farthest? Who has better aim shooting their Straw Rocket at a target? Can you tape a Straw Rocket to the bottom of a paper airplane and launch the airplane with the straw? Will it work if you simply tape a wing (such as a triangular piece of paper) onto the Straw Rocket? Have fun, but be safe!

Flexagons

Flexagons

Here's an interesting thing to make!You need to start with a square piece of paper, which you can make by taking a sheet of paper and folding one corner over to the opposite side as in the picture. Carefully cut off the strip of paper below the triangle that you just created. Save this strip of paper for the Straw Rocket below!
Open up the square piece of paper, then fold it in half.
Fold it in half again.
Open it up, then fold it in half the other way.
Fold it in half again.
Cut out the 4 squares in the middle.Write the numbers in each square as in the picture (some of the numbers will be upside down). On the right-hand side of the picture, notice that the paper is cut between the 2 and the 1.
Turn the paper over and write the numbers in each square as in the picture.In the bottom left corner there is a 6. Fold the paper to the right along the blue line so that the 6 in the corner is on top of the 6 next to it. In the bottom right corner there is a 4. Fold the paper down along the red line so that the 4 in the corner is covered by the 4 above it.
Now the bottom row has 3 1 2 5.Fold down along the blue line so that the 2 is behind the 3. Fold the bottom row to the right along the red line so that it goes behind the 5.
Fold to the right along the blue line so that the 5 on the left covers the 5 next to it.Fold up along the red line so that the 1 goes behind the 2.
Fold to the left along the red line so that the 1 goes behind the 2, then tuck the end so that the 3 on the right (in the picture) is on top of the 3 on the left.
Place a piece of tape at the top of the 2 in the top left corner, then bend the tape behind the 2 so that it sticks to the 1 on the other side.You have finished making your Flexagon! Now you have a square piece of paper with two "faces." One face has the number 2 all over it, and the other face has the number 1 all over it. It's kind of like having dice with only the numbers 1 and 2. Normal dice have 6 faces, but this one only has 2 faces. Or does it?
Your Flexagon has a height and width, which are two dimensions, and it also has a front and back with a tiny bit of depth between them. Therefore it is a three-dimensional object.Now, with the "2" face in front of you (and the "1" face on the other side), bend the Flexagon in the middle as in the picture.
When you bend it all the way back, it will open up at the crease.Where did the "3" face come from? We said that the Flexagon is three-dimensional with a height and a width and two faces (the "1" face and the "2" face), so does this mean that the "3" face appeared out of the fourthdimension?
Turn the Flexagon over so that you're looking at the "2" face again, then "flex" it just like you did above. You should be looking at the "1" face. Turn it over so that you're looking at the "2" face again.Now bend the "2" face in the middle the other way (as in the picture).
Open it at the crease.Where did the "5" face come from? This Flexagon actually has 6 faces, just like regular dice! You can only see two faces at a time, so does this mean that the other four faces are warped into other dimensions until you "flex" them into our third dimension? The prefix "tetra" means "four," and the prefix "hexa" means "six." Since this is a 6-faced, 4-sided Flexagon, it is called a HexaTetraFlexagon. There are lots of other Flexagons you can make (such as DodecaHexaFlexagons, which have 12 faces and 6 sides!), and you can find them by searching the Internet for "flexagon".
Years ago I invented a "FlexaMaze" in which you must follow a line from the Start to the Finish through all of the faces.I used a HexaHexaFlexagon (6 faces and 6 sides), as shown in the picture. I submitted it to Games Magazine years ago, but I have no idea if they ever published it. See if you can make your own FlexaMaze!