Mystery object

Iain’s latest post wins. When the ambient temperature changes, the density of the clear liquid in the cylinder changes - ie if the temperature increases, the particles in the clear liquid move further apart, reducing in density. The glass bulbs all have a different density. Those with a low density will move upwards when the density of the liquid around them decreases. Get it? I’ll show you with my Gallileo thermometer next week. In the meantime, you’ve all won points, both for first, second, and any other attempts. Well done! Check out the points table to see where you are at now.

 I’ll post another question sometime over the weekend.

Mystery object

See my comment. Two of you are so close, but not close enough. Come on the rest of you - let’s have some more involvement!

Dippy drinking bird

Well done Kalum, Iain and Owen. It was indeed the high humidity, resulting in virtually zero evaporation, that caused the bird to stop. Aiming the fan at it forced evaporation to take place. So, a point to each of you. I’ve added a page to the blog - it’s called Competition Points 2009 - where you can check how many points you have earned at any one time. You can access the page at the top of this page. As a bonus to you three keen students, you can earn an extra point next time if you get someone else from your class, who has not previously entered, to enter the next competition. They’ll have to refer to you in their answer.

Dippy drinking bird - the answer

Well done Kalum and Iain. Excellent answers from both of you, so I’m being a real softie and giving you both a canteen voucher - come and see me to claim it. I loved your enthusiasm. Now watch out for the next challenge.

Anyone who wants to see the answer to the question needs to check out the comments that Iain and Kalum posted.

The circuit goes but the switch is off…

Well done Lindsey. The answer is to have a short circuit (containing only a switch) in parallel with the lamp.

Joseph’s Television

The wrong amounts have been added up. The $2 the assistant has kept should be added to the $25 the shopkeeper has, giving a total of $27 - the amount Joseph paid for the television. Joseph has $3, which, added to the $27 makes the total up to $30; the original amount involved.

The half full jar

The amoebas split in two every minute, so if the jar was full at 12 noon, it must have been half full at 11.59 a.m.

Coloured hats

Since there were only 2 blue hats and 3 yellow, the only way that Richard could possibly know the colour of his hat is if the other two were wearing blue hats - so his hat would have to be yellow.

Why do we need leap years?

The time taken for the Earth to make one complete revolution around the Sun is known as a solar year. A solar year doesn’t contain an exact number of days - in fact there are 365.242 days in a solar year. By adding an extra day every leap year, our 365 day calendar doesn’t get out of step with the seasons.

If you’re interested in this and related topics, Katikati Library has recently purchased a book called “Why is Uranus Upside Down and Other Questions About the Universe”. Written by Fred Watson, it was first published in 2007 by Allen and Unwin.

Farmer Brown’s horses

She borrowed a horse. the 18 horses were then divided as follows: the eldest daughter had 9 horses (half of 18), the second eldest had 6 (a third of 18) and the youngest had 2 (a ninth of 18). This left one horse over to return to Farmer Smith.