Topology: Quarters, Dimes, Index Card, Scissors and You

Starting Small: A Quarter Through a Dime-Sized Hole

1. Fold an index card in half, widthwise.
2. Unfold the card and trace a dime so that it is centered on the card. Use the crease as a guideline.
3. Refold the card and cut out the shape of the traced dime.
4. Now that you have a dime-sized hole, try to fit a quarter through it. It's just not possible, right?
5. Here's the trick . . . .  With the card folded along the crease, place the quarter inside of the folded card. Make sure that the quarter is centered on the dime-sized hole you already cut.
6. Grip each of the corners on the folded end of the card with your thumb and index finger. Pull the corners up and watch as the quarter slides out the dime-sized hole.

Going Big: Fitting Through an Index Card

1. Fold an index card in half, lengthwise this time.
2. Unfold the card and cut an incision along the crease that you've created. Don't cut all the way to the either end of the card. Leave 1/8" to 1/4" on each end.
3. Fold the card in half again along the same crease as before.
4. Carefully make a cut at the point your first incision stopped at a 90º angle down towards the open or unfolded side of the card. Again, remember to leave a 1/8" to 1/4" gap.
5. Repeat the previous step, this time starting from the open side of the card, leaving a gap before you get to the other incision.
6. Continue making alternating cuts along the length of the card until you reach the other side.
7. Gently pull the card open by pulling on the two ends of your original crease. The resulting, zig-zagging loop will be big enough to fit over your entire body!

How does it work?

Both of these Index Card Tricks are based on topology. Topology is concerned with continuous deformation of objects and how the way a surface or object is analyzed and manipulated determines how we understand it. Sounds complicated, right? The science of topology shows how you can alter the shape of an object without altering its size.

In the Quarter Through a Dime-Sized Hole experiment, you are able to change the perceived size of the hole without actually altering it. The squeezing and bunching of different areas of the card allow the hole to gain size along the width of the quarter.

In the Fitting Through an Index Card experiment, when you cut the card as the instructions direct you to, you do not remove any part of the card. You simply change the perceived layout in the zig-zagging loop that allows you to fit through it. In both experiments, topology allows you to change the shape or layout, but not the actual size.

SOURCE: Steve Spangler Science

Mysterious Appearing Colors (Benham's Disk)

Video followed by explanation. Source link.

We know that red and blue make purple, blue and yellow make green, and that yellow and red make orange. Most of all, we know that when you mix black and white you get…um…a rainbow. You can use black and white to make actual colors. See just how the spinning illusion can trick your eyes. Materials Printer White paper Craft paper or card stock paper Glue stick Toothpicks Downloadable template Click on the downloadable template and print it out on craft paper or card stock. Cut out one of the four circular designs. Break a toothpick in half and stick one of the halves through the design you cut out. Make sure the pointed end of your toothpick is on the blank side of the disk. You've made a top. Give the top a spin and watch the design on the top. What do you see? Repeat steps 2-4 with the other three circular designs. What do you notice about these designs as they spin? Observations Once you've got the disk spinning, take a look at the circular design on it. What's going on over there? Where did all of those colors come from? *Note* Some of the disks only produce colors at certain speeds, some faster or slower than others. How does it work? Hmmm… how does it work? That's a really good question. We honestly don't know for sure. No one does. But we've got some pretty good guesses. The black and white circular design that you printed out and pasted to your cardboard is called Benham's Disk.  Benham's Disk originated over 100 years ago and, when spun at the right speed, creates a changing pattern of light that is noticeable by your retina.  Many scientists think that the visible pattern of light created by the disk resembles a "code" similar to what the brain receives when the eyes see color. The rapidly spinning black and white disk tricks the brain into seeing the colors. Crazy!

Magic Rollback Can - Transfer of Energy

Potential and kinetic energy at work in this magical demonstration! Video first followed by a description. Source Link

In our long line of "magical" science, we introduce the Magic Rollback Can. The Magic Rollback Can appears to be a normal can of coffee or oats, but after you roll it along the ground a little ways and watch it come back, you'll be wondering just how it works.

Materials

• Coffee or oats can
• Nail or other hard pointed object
• 9-volt battery or object with similar weight
• Rubber band 
• 2 paperclips
• Tape

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1. Using the nail, make a hole in the middle of the bottom of your coffee or oats can. Be extra careful when using sharp objects. Also, if you are using a coffee can, be careful around the sharp metal edges that you may create when making the hole.
2. Poke the same kind of hole in the lid of the can.
3. Tape the 9-volt battery to the middle of the rubber band. Make sure both sides of the rubber band are taped to the bottom of the battery.
4. Push one end of your rubber band loop through the hole in the bottom of the can and secure it there by attaching one of the paperclips. Once you have it secured, tape the paperclip down.
5. Stretch the rubber band across the length of the can and push the other end of the rubber band loop through the hole in the lid.
6. Secure the rubber band with a paperclip and tape it down.
7. Put the lid on the can. Does the battery rub against the side of the can? If not, you're good to go. If it does, try a shorter rubber band.
8. Getting the set-up just right may take a bit of experimentation, but you'll get it!
9. Set the can on its side on a hard surface or short carpet floor and give it a roll. Once the can comes to a stop, try to contain your excitement as it begins to roll back to you!

How does it work?

The Magic Rollback Can is a great example of transfer of energy. When you roll the can, it has kinetic energy. As it slows down, the energy is transferred into potential energy within the twisted rubber band inside the can. The twisted rubber band's potential energy is then transferred back to the can in kinetic energy as it untwists.

The secret to all this energy transfer comes from the weight that you've taped to the rubber band inside the can. While the weight is being pulled down by gravity, it is also being subjected to a twisting force from the rubber band. So long as the force being exerted by gravity on the weight is greater than the twisting rubber band's force on the weight (meaning the weight never goes over the rubber band), the rubber band will continue to twist.

Once all of the kinetic energy from the rolling can has been exhausted by converting to heat (friction) or potential energy (twisted rubber band), the can stops rolling and the weighted rubber band is able to unwind. Because of the weight in the middle of the rubber band, only the ends of the loop are able to unwind and, therefore, the can begins to roll backwards.

Additional Info

If you are looking to take the Magic Rollback Can to the next level, try painting it a solid color. If you do this, observers won't be able to see the apparatus on the ends of the can. This makes the Magic Rollback Can a perfect "Black Box" tool for teachers. Show your students what the Magic Rollback Can does, and have them observe and hypothesize how the can might work.

Berry pH Paper

A homemade litmus test to detect acids and bases

No longer must you search for specialty litmus paper. Here is  a formula that will allow you to create your own acid and base detecting litmus paper using little more than a bit of fruit.

Materials

• 1/2 cup of blackberries
• 1/4 cup of water
• 2 tablespoons of dish soap
• 1/4 cup of vinegar
• Bowls or other containers
• Water
• Scissors
• White construction paper
• Paper towels
• Zipper lock bag

Making the Paper

1. Remove any stems or leaves from your berries and place the berries in a zipper lock bag.
2. Zip up the bag and mash and mush your berries until they look like jam.
3. Add a small amount of water to thin the juice a bit.
4. Mix it all up and pour your berry liquid into a bowl.
5. Cut some thin strips of the white construction paper and dip them into your mashed berries. Push the strips all the way into the berry mush to make sure they are good and coated with the juice.
6. After taking your "berry" well-soaked paper out of the juice, pull the strips between your thumb and index finger to remove any excess juice and pulp.
7. Lay the strips onto paper towels and allow them to dry.
8. Once your paper strips have dried, carefully pick off any large pieces of pulp or berry skins. You're ready to use your Berry pH Paper.

Putting Your "Berry" Own pH Paper to the Test

1. Pour 1/4 cup of water into a bowl and mix in two tablespoons of dish soap.
2. In a separate bowl, pour 1/4 cup of vinegar.
3. Dip half of one strip of your Berry pH Paper into the bowl containing dish soap and water. Do the same thing with another strip of Berry pH Paper, but this time dip it into the vinegar.
4. Set the Berry pH Paper strips onto a piece of paper towel to dry. This should only take about five minutes. Make sure you label the pH strips to remember which strip was dipped in which liquid.
5. What color changes did you notice? Which liquid was an acid? Which liquid was a base?

Cool... but how do I use it?
Blackberry pH Paper turns pinkish red in acids and turns deep purple in bases.

How does it work?

Blackberries, blueberries, strawberries, and a bunch of other flowers, leaves, and stems are naturally occurring pH indicators. This is true because they contain chemicals from the anthocyanin family of compounds. Anthocyanin compounds turn red in acids and blue in bases when they are in their pure form. In this case, we have the anthocyanin compounds within the juice of the berries. This results in a less distinct, but still distinguishable, color change.

Additional Info

Try testing out other liquids like milk, soda, or fruit drinks to find out which ones are acidic and which ones are basic. 

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