This week's activity comes from Jason Morvan who works at our CSIRO Science Education Centre in Sydney. It could be the most challenging Science by Email yet. Jason assures us that once you have mastered it, you will amaze your friends and win over your enemies.
Warning: This experiment involves an unstable glass. Don't use expensive or precious glasses and be ready to catch the glass if it falls. If an accident does happen, clean up any broken glass thoroughly.
You will need
An old twenty cent coin. The coin needs to have the picture of the Queen's head that includes her neck and shoulders. Later versions of the coin only have the Queen's head.
A glass of water about ½ to ¾ full.
What to do
Place the twenty-cent coin on the table with the Queen's head facing up.
Place the edge of the glass in the groove that appears below the shoulders of the Queen and the rim of the coin.
Angle your glass and try and find the point at which the glass remains balanced.
Tips from Jason
NEVER GIVE UP! It may seem that after about 30 or 40 seconds of attempting this experiment, that you've been trying for hours, but keep going, you'll get it eventually.
There is a point on the Queen's image that is closer to the rim than the rest of her body, towards her back - use that as the point you try to balance the glass on.
You can do using any glass, but a glass similar to the ones they use for beer will probably be easier for your first attempt.
See tip one.
What's happening?
This is a simple balance activity. The groove in the coin keeps the cup stable while you find the balance point, about which, the weight of the glass and water on one side of the pivot point, is equal to the weight on the other side.
All objects have what is called a balance point or centre of mass. When the balance point is directly above a point, an item will balance on that point. The shape of an object and how weight is distributed all change where the centre of mass is.
The same thing applies to any balancing object, including a person standing (balancing) on their two feet. An average person's balance point sits somewhere level to their belly button about half way between front and back. If you stand up, you can balance easily so long as that point is above your feet, but try and move so it isn't and you'll start to topple.
Applications
When we were learning to walk we had to learn to keep our balance point within the area of our support base or we would fall over. A sumo wrestler spreads their legs wide and crouches before they clash with their opponent. By widening their support base and lowering their balance point, a sumo wrestler becomes more stable.
Second challenge
Balance three empty glasses on top of each other on their rims, without the help of any other object. Make sure the glasses are empty and identical. The main secret is that if you imagine a clock face when you look at the glasses from above you must remember ten o'clock and two o'clock. Directly in front of you would be twelve o'clock. Place your first glass down onto the table. Place the second glass on top of the first glass in the position of ten o'clock. Find the balance point. Now place the third glass on top of the second glass in the two o'clock position. This trick will take a bit of practice, but when you get it right a few times it gets easier.
This could be the most challenging Science by Email activity yet.
The coin needs to have the picture of the Queen's head that includes her neck and shoulders. The coin on the right is the coin you need to use for this activity.
Never give up. It may seem that after 40 seconds of attempting this activity, that you've been trying for hours, but keep going, you'll get it eventually.
This is the face of delight when you get the balance just right. To learn more amazing science or have a session at your school contact your local CSIRO Science Education Centre.
