Homemade Juggling Balls

They cost next to nothing and look great, and they're perfect for learning how to juggle.

1. Pour about half a cup of rice* into an empty water or soft drink bottle (if you don't have a funnel, make one from the top of a second bottle).




* The size of your juggling balls depends on the amount of rice you use.

 
 
 
 
 
 
 
 
2. Inflate a balloon to about the size of a grapefruit, twist the neck and stretch it over the neck of the bottle
 

 
 
 
 
 
 
 
 
3. Turn the bottle upside down so all the rice falls into the inflated balloon – then remove the balloon from the bottle and let it deflate.

 
 
 
 
 
 
 
 
4. Cut the neck off the balloon – the rice will stay in the balloon.

 
 
 
 
 
 
 
 
5. Cut the neck off a second balloon and stretch it over the hole to seal the rice into your juggling ball.




You could use the ball like this, but they look heaps better if you add more balloons for some patterns and colour.

 
 
 
 
 
 
 
 
6. Cut the neck and a piece of the top off a third balloon and stretch it over the ball to get a single stripe of colour.

 
 
 
 
 
 
 
 
7. You can cut lots of very small holes in a balloon by pinching it between your finger and thumb and carefully cutting off the tips – remove the neck and stretch over a ball to make spotty patterns.

 
 
 
 
 
 
 
 
8. Done! You’ve just made some fantastic juggling balls … now all you have to do is learn how to juggle!

Freaky Ice Hand

Here’s a great way to waste a dishwashing glove... fill it with coloured water and make a freaky frozen hand to wreak havoc with.

1. Trim the glove so that the fingertips hang just above the bottom of the jug / container.

 
 
 
 
 
 
 
 
2. Push two shish kebab skewers through the wrist of the glove and at right angles to each other.

 
 
 
 
 
 
 
3. Hang the glove in the jug / container.




Note: if you want to be able to hold your frozen hand like an ice block, secure a stick to the skewers

 
 
 
 
 
 
 
 
4. Pour coloured water into the glove.




Note: food colour tends to concentrate in the centre of ice blocks as they freeze so I used about 15 big drops – be careful not to put stains all over the place!

 
 
 
 
 
 
 
 
5. Place the jug / container in the freezer (you may need to remove the shelf for it to fit) and wait for at least 8 hours.

 
 
 
 
 
 
 
 
6. Nearly finished! Carefully cut and remove the glove – do this in the sink or over a bucket.




Note: the fingers break off very easily so be extra careful – if you’re quick, you can refreeze snapped fingers back on.

 
 
 
 
 
 
 
 
7. Your freaky ice hand is ready for shananagans – what you do with it from here is your business.




Note: be careful with the drips which will stain carpets etc – best to keep your ice hand outside!

 
 
 
 
 
 
 
 
8. I tried to get to know my ice hand but it kept giving me the cold shoulder! Get it? Cold ... shoulder? Ahem.

Vortex Rings

What do dolphins, humans and volcanoes have in common? They can all produce toroidal vortices of course! Surprised? Grab some food colour and a glass of water to find out how.

1. Fill a tall glass to the brim with water and wait for at least 30 seconds. Even though it looks still, water keeps swirling for ages so the longer you wait the better.




HINT: Use an eye-dropper if your food colouring is not the squeeze bottle type.

 
 
 
 
 
 
 
 
2. Squeeze gently so a drop of food colour is dangling from the tip of the bottle. Touch the water surface with the drop.

 
 
 
 
 
 
 
 
3. Wow! The drop of food colour shoots down into the water and almost instantly turns into a tiny little donut!

 
 
 
 
 
 
 
 
4. Look closely and you’ll see the donut is swirling in on itself as it descends. While it’s moving quickly, the ring is very stable and retains its shape.

 
 
 
 
 
 
 
 
5. As it descends and slows down, the donut suddenly becomes unstable and breaks up - it's called a vortex breakdown. If your water was still enough, a beautiful inverted crown might form. The tips of the crown are even smaller vortex rings.

 
 
 
 
 
 
 
 
what's going on?


A vortex is formed when a fluid swirls around a central point. Whirlpools and tornadoes are two familiar types of funnel shaped vortexes (or vortices). The mathematical name for a donut or ring shape is a toroid. So, you’ve just created a miniature toroidal vortex... cool!!!



Toroidal vortices form due to a complicated combination of friction and pressure. Friction between the drop of food colour and the water is what slows its descent. But the friction is not equal on all parts of the drop. The ‘sides’ experience a sideways or shearing friction. The very bottom of the drop meets the water head on and so experiences more friction. But the little drop also leaves a little wake of lower pressure behind it. The differences in pressure and friction deform the drop into the swirling donut shape.



The clear water inside the coloured ring is called the vortex core. You’ll notice that vortex rings are quite stable until they slow down. At some critical speed, the core enlarges very suddenly and the ring breaks apart. This phenomenon is called a vortex breakdown. Vortex breakdowns are not yet fully understood but are of particular interest to aeronautical engineers and combustion scientists. A sudden change or breakdown in the structure of vortex rings above a wing can have detrimental effects on the aircraft’s performance. On the other hand, vortex breakdowns inside combustion chambers are highly desirable because they mix air and fuel more thoroughly. Check out the link below to see some spectacular videos of vortex ring experiments conducted by Dr TT Lim of the National University of Singapore. There are videos of vortex rings colliding and even playing leap frog! Super cool!!!



But humans aren’t the only creatures capable of making and enjoying vortex rings. Dolphins can blow perfect air bubble vortex rings too. These are not to be confused with the large bubble nets some whales and dolphins make by swimming in a large circle while blowing air bubbles to round up fish. Bubble rings are small toroidal vortices made of air which dolphins make and play with. They watch and chase them and even use their flippers to stop them rising in what appear to be games similar to those we humans play with soap bubbles. Check out the link below to see photos of this behaviour! Ultra cool!!!



But the biggest vortex rings on Earth are not made by dolphins or humans. Volcanoes sometimes emit huge ring shaped clouds of steam and gas up to 200 metres in diameter. How they are formed is still a mystery but they can fly up to 1000 metres high and last more than 10 minutes. Check out the story and photos of Mt Etna's gigantic vortex rings below. Mega cool!!!

Marble Gravitron

1. This is very important: it only works with a glass that is narrower at the top like the one on the left in this picture. Wine glasses work best - the glass on the right in this picture won't work at all.

2. Trap a marble (or any spherical object) under the glass on a smooth surface.

3. Wiggle the glass and the marble will start rolling around inside really fast. Look carefully and you'll see it starts 'climbing the walls'.


Note: the marble is just a faint blur in this photo

4. When the marble is really hooting along, lift up the glass and the marble stays inside. With some glasses, you can keep the marble inside as long as you keep wiggling.


Note: you can just see the blur of the marble between my middle and ring fingers in this photo.

Linked Paper Clips

Fold a dollar bill (or any piece of paper) one-third of the way, then attach a paper clip to it.

Fold the other side, then attach a paper clip to it.

Slowly pull the edges of the dollar bill apart.

The picture on the right shows the dollar bill when its edges are pulled almost all the way apart.

When the dollar bill is fully straightened out, the paper clips will fly up into the air, linked together!

Make sure to aim the paper clips away from people!

The "Four Fours" Game

Here's an interesting game for older kids. Play it on car trips, in a restaurant while waiting for your food, and so on.

To play this game, try to make the numbers from 0 to 20 (and beyond, if possible) using exactly 4 fours and any math operations that you can think of.

Math operations are things like plus, minus, multiply, divide, square root, to the power of, and so on.

The examples on the right demonstrate some ways of making 0 using exactly 4 fours.

Remember, you can only use the number 4, and you must always use 4 of the number 4 (no more, no less).

We've given you some ideas for making 0, can you make the numbers from 1 to 20 and beyond? It's tricky!