Re: How does a water-wiggle work? How does the hose move by itself?

Greetings, Wyndi:

I confess I had to search for a water wiggle, to be sure I knew what you were Asking about. For anyone else who doesn't happen to know/remember what a water wiggle is, look here. After the page loads, scroll down to find the pictures. Please note that this toy is considered to be dangerous, and was recalled from the marketplace years ago.

Wyndi, I hope we are indeed referring to the same thing. If so, I do have an Answer for your Question, which begins with something that is often called "The Law of Action and Reaction". This Law states, "For every action, there is an equal and opposite reaction." In the water wiggle, water is spewing of it's "head" in some direction, so the head has to move in the opposite direction.

Perhaps you would like to know a little more about how that Law works. Think about a balloon that you have just filled with air. You are holding the balloon closed, so the air does not escape. As you know, if the air did escape, the balloon would shrink back down to its original small size. Scientists say that the body of the inflated balloon is applying a "force" to the air inside the balloon. The air is squeezed by this force, and resists. The air is applying an opposite force to the body of the balloon, from insidethe balloon. As long as you hold the balloon closed, these two forces are balanced, and the balloon doesn't shrink, and it doesn't expand.

One important thing to remember is that the air inside the balloon is applying its force to ALL of the inside surface of the balloon. Every part of the inside of the balloon is being pushed with the same force, by the squeezed air. Because this is also a balanced force, the balloon keeps the same shape -- it does not (by itself) bulge outwards HERE for a moment, and then bulge outwards THERE for a moment, and then bulge out somewhere else....

When you finally let the balloon go, the opening lets the air out and the balloon whizzes around for a few seconds, much like a water wiggle. This happens because the air inside the balloon is pushing ALL directions inside the balloon. The opening that lets the air out has allowed the force inside the balloon to become UNbalanced. And so the force of the air inside the balloon can push air out the opening in one direction (Action!), AND push the whole balloon around in the other direction (Reaction!).

It is a simple fact that whenever any force is causing something to happen, it is also causing something else to happen. When you bend your legs and then jump into the air, you are pushing yourself away from the Earth (Action!)-- AND you are pushing the Earth away from you (Reaction!). It's just because the Earth is so much bigger than you, that you don't see the Earth move when you do this. Usually, the bigger something is, the harder it is to move, as you know.

Back to the water wiggle. It is attached to a garden hose, and you probably know that when water flows out the plain end of a garden hose, you can make it flow faster by holding it in your fist, and putting your thumb over the end. You are applying a force to keep your thumb there, actually squeezing against the water in the hose. The smaller opening, with your thumb in the way, does not let the water flow out of the hose very easily, but because extra force is now present, from your thumb, the water comes out of the hose faster. Perhaps you have seen nozzles that can be screwed onto the end of the hose, that let you adjust the flow of water faster or slower. Inside the water wiggle is a nozzle that causes the water coming out of the hose to flow faster. This water hits the inside of the head of the water wiggle, and bounces off. Since the water can keep moving away from the head of the water wiggle, this hitting and bouncing is an unbalanced force, just like the one inside the whizzing balloon. It causes the water to go one way (Action!), and the head of the water wiggle to go the opposite way (Reaction!). And, since the head of the water wiggle is still attached to the hose, the moving head carries the end of the hose along with it. Well, since the end of the hose still sprays water inside the head of the water wiggle, for as long as the faucet is turned on, Action and Reaction keeps causing the thing to just keep on moving!

Now where do all the wiggles come from? I'm sure you want to know the Answer to that, too. Let's start by thinking about a stack of blocks for a minute. If all the blocks are the same size, how tall a stack can you build, before it falls over? Why does this always happen? Well, think about the BOTTOM block of the stack -- when you set the next block on top of it, you have to put it pretty much in the middle of the bottom block. Otherwise the upper block will simply fall off the edge of the bottom block. This simple fact is true for ALL the blocks in the stack. Now, when the stack is tall, can you be REALLY SURE that you are putting the top block directly over the middle of the bottom block? It is hard to tell, when they aren't next to each other! So, eventually, you always miss the middle of the bottom block, when adding a new top block. That's when the stack starts to tip....

Anyway, in order for the water wiggle to move in a perfectly straight line, the water has to spew out in a very exact direction, in relation to the head of the toy, and the attached hose. Since the water DOESN'T spray out anywhere near such a perfect direction, the head of the water wiggle is constantly doing something much like your stack of blocks falling over. Since the toy is all one piece, it can KEEP "falling over", for as long as the faucet is turned on. Clearly, if the head of the toy isn't moving straight, it must be starting to wiggle!

The last key piece of information is the fact that the more the head of the toy just happens to move in any one direction, the more weight of hose the head has to drag behind it, to keep moving in that direction. Well, when the weight of dragged hose increases (Action!), this causes the head of the water wiggle to start to "aim" in a new direction (Reaction!). So, the head is always moving simply because of the water spraying from it, and the direction it moves is always changing, because of the hose it drags along. And that's how a water wiggle works.