At some time in your life, you have probably heard that in a fall, cats always land on their feet. Is that true? Well, usually it is. Cats have the amazing ability to turn themselves right side up as they are falling. That does not mean that a fall will not injure them. If you fell off a tall building, would landing on your feet keep you from being injured? No. The same is true for cats. Landing on their feet lets their legs flex to absorb some of the impact, and keeps the impact from directly hitting more delicate bones, but cats do not have any magical protection against injury from falling.

What is amazing is the way that they perform this trick of landing on their feet. They do it by combining fast reflexes with the laws of physics. To get an idea of how they do it, you will need:

• a chair that swivels easily. Common office chairs work very well for this.
• an open area with plenty of room, so you don't break any lamps, furniture, or legs.

OK, lets start by thinking about what the cat has to accomplish. It is falling, which means that it does not have anything to push or pull on to turn itself. Instead of falling, you can get an idea of the problem that they face by sitting in the swivel chair. Make sure that you have plenty of open space around you by holding your feet straight out and turning in a complete circle. You want at least a foot or two of open space between your feet and the closest thing you could bump into.

Now lets get an idea of the challenge the cat faces. Sit cross legged in the chair, so your feet do not stick out. Put your arms in your lap, with your elbows tucked in against your side. Your challenge is to turn the chair around so that you are facing the opposite direction by twisting your body from side to side. Don't move your arms or legs. You can twist at the waist and your neck, but nothing else. DON'T HURT YOURSELF! You will find that you can turn the chair slightly to the right by twisting your body to the left. The problem is that when you twist back to the right, the chair spins back to the left, winding up back where it started. Wiggling the chair back and forth is no problem, but you don't get very far towards turning the chair around.

To see how the cat manages its trick, lets try something different. Keep your elbows at your side, but extend your hands out to the side. Then try twisting again. This time you will notice that the same motions cause you to swivel back and forth farther. Extend your arms all the way out, and try it again. Now, you are really moving back and forth. As you move your arms further and farther from your body, you can use their inertia (resistance to changes in motion) to push against.

You still have the problem that you are twisting back and forth. Remember that you are a falling cat, and you need to turn yourself so you can land on your feet. That leads us to your next step.

Extend your arms all the way out, and then twist to your left. That swivels the chair and your body to the right. Now, before you twist the other direction, pull your arms back in close to your body. Since your arms are in close, you can turn back without swiveling the chair back in the other direction. You have turned part of the way around, and you are back into the position to do it again. Extend your arms again, and repeat the process. It took me three arm swings to turn my chair around so that I was facing in the opposite direction.

Cats do this maneuver even better because they are incredibly flexible. They extend their front legs while pulling in their back legs, and then twist in the direction they want to turn. Very quickly, they pull in their front legs, and extend their back legs, making another quick twist that lets them wind up facing as much as 180° from their original direction.

Although cats are incredibly fast at this, it still takes time. Cats that fall from a very short distance do not have enough time to twist around. Also remember that landing on their feet does not mean that they don't get hurt during a fall. Their reflexes and flexibility can help them land in the best position, but they can still suffer injuries and broken bones from a fall; so you should not use your cat as an experimental subject.

If you want to experiment further, try holding a weight in each hand as you do the experiment. Do you think that will make it work better or worse? Try experimenting with different arm motions. I had interesting results from making the same motions that you would use for paddling a canoe.

Link to Whistle Stick, part 1

I hope that you made your own Whistle Stick, and have been playing...., I mean experimenting with it. I also hope that you spent some time thinking about the science behind the sound that it makes, because that is what we are going to explore this time. For your exploration, you will need:

- a wooden spoon
- a large container of water
- the Whistle Stick from last week

It's always good to start with the basics, so begin by thinking about sounds in general. We hear a sound because of waves traveling through the air. Just as dropping a stone into a pond causes waves to spread out across the water, popping a balloon, vibrating a guitar string, or singing a song causes waves to spread through the air. When those waves hit our ear drums, we hear the sound. That means that the Whistle Stick must be producing waves in the air. But how? That is where the wooden spoon comes in. We will use it in place of the popsicle stick, and look at waves in water instead of air. Hold the wooden spoon between your palms, with the end of the spoon in a container of water.
Slide your palms to twirl the spoon slowly in the water. As the spoon spins, it makes waves in the water. Try spinning it at different speeds, noticing how that changes the distance between the waves. What you should notice is that as the spoon twirls, it pushes on the water to send out a wave. As you spin the spoon faster and faster, it makes more waves, and those waves get closer and closer together.
Now lets think about sound waves. The picture at the right shows a graph of the sound produced by the whistle stick. Notice that at the start of the sound, it reaches far up graph. The higher up the graph it goes, the closer together the sound waves are, and the higher the pitch of the sound. If you click the picture, you can watch a short video, letting you hear the sound, seeing how the changing sound matches the graph.
It is much easier to see (and hear) if we slow things down. This graph shows the same sound, stretched out four times longer than the original. That lets us see the curve as the pitch falls. Again, you can click the picture to watch a short video. Because it plays the sound slower, it is easier to see (and hear) that the sound begins with a high pitch (waves very close together), and then the pitch falls as the waves get farther apart.

Now lets put that all together. Like the wooden spoon, the faster the popsicle stick spins, the closer together the waves will be, and the higher the pitch of its sound. When you first snap your fingers, the Whistle Stick spins very fast, making a high pitched sound. As it pushes against the air to produce those waves, it gives up some of its energy of motion. That causes it to spin slower, producing a lower pitched sound. Looking at the graph, we can see that the rate of spin slows very quickly at first, and then more gradually.

If you remember from last week, I also made a Whistle Stick from a tongue depressor that was much wider. it made a much lower pitched sound, that did not last nearly as long. Why? The wider blade had to push against more air, transferring the energy of motion much faster, causing the speed of its spinning to drop much faster.

If you want to do some experimenting, you might try cutting notches into the sides of the stick or doing other things to change its shape. Do you think that would change the sound? Sounds like a good reason to eat more popsicles to me.

Three Holes, part 2

Hopefully, you spent quite a bit of time thinking about last week's experiment, and more importantly, performing the experiment to see if you were correct. If not, before you read any more, GO TRY IT! If you don't, you are missing out on the actual fun of scientific investigation. This week, you will need:

- the same materials that we used in part 1.
- 3 more bottles
- some wooden blocks or other things to change the height of the bottles

If you did try it, you probably got results similar to what you see in the photo below.

If you did try it, you found that the water stream from the middle hole hit at the greatest distance from the bottle. Why? To understand that, we need to look at the variables involved with each of the three streams.

Variable? What is that? It is something that can change from one test to another. If we think of the three holes as three different tests, then the variables are the things that change from one to another.

The first variable is the water pressure, and that varies according to the depth of the water. The deeper the water, the greater the pressure. That means that the top hole will have the least water pressure, and the bottom hole will have the greatest water pressure. Then why didn't the bottom stream go the farthest? Because there is another variable involved.

What else is different for each stream, besides the water pressure? The distance that they have to fall to hit the surface! If that distance is too short, the stream when it could still travel much further from the bottle. The top stream has a longer distance to fall, giving it a longer time to move away from the bottle. The bottom stream has the shortest distance to fall, so it has the least time to move away from the bottle.

Looking at the three streams, the bottom one has the most water pressure, but not very far to fall before it hits the surface. The top stream has the least water pressure, but a long way to go before it hits. The middle stream has more pressure than the top, and more distance to fall than the bottom. That combination lets it hit the farthest from the bottle.

Is there a way that we can compare those variables? Easy! All we have to do is to control one of those variables.

Which will go farther?

You could control the water pressure by using three bottles that each had a hole at the same depth. By placing the bottles on top of blocks, you could arrange them so that the three streams were at different heights. With the same pressure for each, the highest stream would go farther, since it has the longest time to travel away from the bottle before it hits the surface.

Which will go farther this time?

You could control the distance the water has to fall by using three bottles again, but this time, make a hole near the bottom of one, near the middle of the second, and near the top of the third. Then place them on blocks so that the three streams are all the same distance from the surface. This time, the stream with the most water pressure (nearest the bottom of the bottle) will go farther.

From there, you can gradually change the height of the blocks until all three bottles were the same height. That would bring you back to where we started, with the middle stream reaching the farthest. With careful testing, you would probably find that the maximum distance would not be at exactly the middle of the bottle, since one variable may make a larger difference than the other. If one is causing more difference, which do you think it is? You'll have to try it yourself to find out.

Have a wonder-filled week.

Link to Part 2

Link to Part 3

What really keeps the water inside this inverted glass?

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For this week's experiment, I wanted something that related to hurricanes. I settled for one that is based on fast moving air and differences in air pressure. You will need:

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Don't let the title fool you. This experiment does not involve any explosions. Instead, we are going to explore the science of resonance. Resonance involves putting in small amounts of energy, at just the right time, to get more effect. A good example is pushing a swing. Each push causes the person in the swing to go higher. We will lift a phone book high into the air by blowing on it.

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How can you make a dollar bill stronger? With science!

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Pull downwards on the string, and use science to cause it to break either above or below the book.

Why is half a water balloon different from a full one?

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Why do balloons act crazy in your car?

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How fast can you throw a piece of paper?

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A flame that seems to move in the wrong direction. Why?

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Use science to make a coin seem to magically rise from a matchbox.

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