The invisible rod

Two similiar acrylic rods are placed in two different liquid. The one of the right is water, the one on the left is corn syrup. Why couldn't the submerged portion of the rod be seen in the jar on the left?

A potential CE lesson material on responsibility, integrity, RESPECT...and self-control

I didn't find this video funny but am rather apalled by the behaviour of both the girl and the raging teen..... I really do hope my students are way better than them, right?

A nice way to start the holidays....

..is to have a good DotA game with my former Sec 2s!

So my current Sec 2s, I'm waiting... :)

Cambodia Service Learning Video - draft version

After much work., finally it's almost done!

Extended version will include bloopers and more....

MYE 2010 results for my classes

Update 12 May 2010: Results for my Sec 3 Exp class is in. Not good at all...


Except for my Sec 3s where I wasn't the marker of their papers, here are the consolidated results for MYE 2010.

Click on image to enlarge:










Keep up the good effort 2A and 2F!

2C, you need to reflect what went wrong this time.... ask more questions in class! Copy down what I've said! Do a bit of memorising!

2B, quite a lot of careless mistakes but nonetheless quite well done. Failures please buck up...this is your streaming year!

3I better wake up! Grrr......

Game for Physics - 99 Bricks

How often does a teacher encourages you to play games? But here I am, recommending this brilliant online flash game called 99 Bricks.

It's essentially Tetris with a twist: the aim is to build the TALLEST structure! However, the bricks observe the laws of stability, momentum, balance of moments, forces due to weight and centre of gravity etc etc....

Link: http://www.kongregate.com/games/WeirdBeardGames/99-bricks

Spending time on youtube

Despite my busy schedule, I've been spending some time on Youtube. Partly because I'm finding interesting clips to share with my students, partly to find some inspiration for the contestants of the Amazing Science X Challenge (http://www.asxc.com.sg/).

Anyway, here's one that I really like. It's by Steve Spangler, on a popular talkshow by Ellen Degeneres.

Watch the first one here! Go check out his other videos too.!

HOM Brain Teasers

Submit your answers to me (for my mentor class 2A) by next HOM Lesson on 08 Mar 2010 and the first 8 students with the complete correct answer will win a prize!

The Questions:

1. You have a fox, a chicken and a sack of grain. You must cross a river with only one of them at a time. If you leave the fox with the chicken he will eat it; if you leave the chicken with the grain he will eat it. How can you get all three across safely?
   
2. What is special about the following sequence of numbers?8 5 4 9 1 7 6 10 3 2 0
   
3. Three travelers register at a hotel and are told that their rooms will cost $10 each so they pay $30. Later the clerk realizes that he made a mistake and should have only charged them $25. He gives a bellboy $5 to return to them but the bellboy is dishonest and gives them each only $1, keeping $2 for himself. So the men actually spent $27 and the bellboy kept $2 - what happened to the other dollar of the original $30?
   
4. You are the bus driver. At your first stop, you pick up 29 people. On your second stop, 18 of those 29 people get off, and at the same time 10 new passengers arrive. At your next stop, 3 of those 10 passengers get off, and 13 new passengers come on. On your fourth stop 4 of the remaining 10 passengers get off, 6 of those new 13 passengers get off as well, then 17 new passengers get on. What is the color of the bus driver's eyes?
   
5. An 18-wheeler truck is crossing a 4 kilometer bridge that can only support 10,000 kilograms and that's exactly how much the rig weighs. Halfway across the bridge a 30 gram sparrow lands on the cab, but the bridge doesn't collapse. Why not?
   
6. A completely black dog was strolling down Main Street during a total blackout affecting the entire town. Not a single streetlight had been on for hours. Just as the dog was crossing the middle line a Buick Skylark with 2 broken headlights speedily approaches his position, but manages to swerve out of the way just in time. How could the driver have possibly seen the dog to swerve in time?
   
7. In a small cabin in the woods, two men lay dead. The cabin itself is not burned, but the forest all around is burned to cinders. How did the men die?
   
8. Ida puts her coffee into the microwave, as she does every morning, for exactly 2 minutes. When the microwave goes off, she opens the door, but then closes the door again and sets the microwave for 2 more seconds. What good would 2 more seconds be?
   
9. I am the owner of a pet store. If I put in one canary per cage, I have one bird too many. If I put in two canaries per cage, I have one cage too many. How many cages and canaries do I have?
   
10. My daughter has many sisters. She has as many sisters as she has brothers. Each of her brothers has twice as many sisters as brothers. How many sons and daughters do I have?
    
11. What seven-letter word has hundreds of letters in it?
    
12. Tom's mother has three children. One is named April, one is named May. What is the third one named?
    
13. Two women apply for a job. They are identical. They have the same mother, father and birthday. The interviewer asks, "Are you twins?" to which they honestly reply, "No".How is this possible?
    
14. A boat has a ladder that has six rungs. Each rung is one foot apart. The bottom rung is one foot from the water. The tide rises at 12 inches every 15 minutes. High tide peaks in one hour.When the tide is at its highest, how many rungs are under water?
    
15. During WWII, there was a bridge connecting Germany and Switzerland, and on the German side, there was a sentry tower with a guard in it. He would come out every three minutes to check on the bridge, and he had orders to turn back anyone who tried to get into Germany, and shoot anyone trying to escape without a pass. There was a woman who desperately needed to get into Switzerland, and she knew she didn't have time to get a pass. It would take her at least six minutes to cross the bridge, but she managed to do it. How?
    
16. A man is traveling with a fox and two chickens, if he leaves the fox alone with the chickens the fox will eat the chickens. He comes to a river and needs to cross it, he finds a small boat that can carry only him and one animal, how does he get himself, the fox and two chickens across the river safely?
    
17. A man and his son had a terrible car accident and were rushed to the hospital. The man died on the way, but the son was still alive and a surgeon was called in to operate. However, the surgeon saw the young boy and said, "I can't operate on this boy. He's my son."How is this possible?
    
18. Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"How did he know his companion was smiling?
    
19. You're riding a horse. To the right of you is a cliff and in front of you is an elephant going the same pace as you and you can't overtake it. To the left of you is a hippo running at the same speed and behind you is a lion chasing you. How do you get to safety?
    
20. If eggs are 12¢ a dozen, how much would it cost for 100 eggs?

Service Learning: Sec 2A 2010 (My First Skool) - 26 Feb 2010

More photos at : http://www.4shared.com/dir/32671992/75bebfd9/Service_Learning_-_My_First_Sk.html

And a video below!

Just for humor...

Created using www.batmancomic.info

Brain Teaser

You have 12 pearls. 11 of them are real, and 1 of them is fake. They all look/feel/everything EXACTLY the same, the only difference between the real and fake ones is their density.

You are given a balance scale (one of those old school scales that compare weights. You can weigh/compare the pearls three (3) times. Describe how you would:

1) determine the fake pearl

2) determine whether the fake pearl is more or less dense than the real pearls.

Post your answer in the comments!

Combine Science (Physics) vs Pure Physics

This is a question from this year's (2009) O-Level Physics (i.e. pure physics)


And this is a similiar question in 2009's O-Level Science Physics

The difference is not in the content nor the depth of knowledge required but the answering skills and the level of understanding for both the content as well as the question.

Sec 2 Exp Physics - "Global Culling Blade"

Top score: 46/50.

Total 69 failures (28%)

As mentioned before, the EOY paper will be tough, and there is no other way about it because we need the results for streaming.

So students who haven't been paying much attention in class or following through the assignments timely will find the paper very hard to handle. Even conscientious students may struggle, due to the limited time (1 hr) and the very narrow margin for any error or slight doubts in your Physics concepts.

I mention this before: "If you simply study the notes we gave you and go for a Physics test, you will FAIL." There's some element of practice but mainly you need to question the theory and truly understand just what the hell this equation/law/rule is talking about.

My last piece of advice is to NOT forget all the Physics you have learnt in Sec 2, because they will be tested again in Sec 3! Regardless if you're in a Pure Physics class or a Combined Science class...

All the best! Enjoy your break...while you can!

2F 2009 class photos

Bridge Challenge @ Ngee Ann 2009

Kranji Sec sent 2 teams of 8 students to take part in the Bridge Challenge 2009 organised by Ngee Ann Polytechnic. The aim was to build the strongest and lightest bridge within 6 hours, using bamboo skewers, vaguard sheet, limited string and glue.

These are the rules of the competition:

Materials
On Day 1of the competition, every team will be given the
following materials for their use:

8” Satay sticks (Pack of 180 sticks) - 5 packs
Ball string - 2 m
630 x 510 mm Vanguard sheet - 2 pcs
A4 paper - 2 pcs
4” x 5/16” Glue sticks (Pack of 12 sticks) - 1 pack


Dimensions
The bridge must span across two supports placed 600 mm apart (the width of each bridge support is 50 mm). The bridge may span straight from one support to the other. The width of the bridge must be at least 150 mm throughout the entire span. There is no limit to the height of bridge.


Judging Criteria
- Strength factor [Failure Load/(weight of bridge +
penalty weight)] 50%
- Design (Structural concept) 15%
- Construction (Workmanship) 15%
- Aesthetics & Innovation (Profile, shape and etc) 15%
- Fact Sheet 5%

The participants

Team 1:

1. Yow Kai En (3B)
2. Foo Chuan Ri (3A)
3. Grayson Chang Fanyao (3D)
4. Jasmend Yow (3F)

Team 2:

1. Yap Hong Yi Desmond (3A)
2. Ng Shao Hui (3B)
3. Tham Chin Siong (3B)
4. Quek Hong Wei (3A)

Pre-Competition

We started preparing only after Common Test. I foolishly thought with 3 weeks, it should be more than sufficient to prepare for the competition.

Unfortunately, I was rudely surprised at the slow pace of work the teams are producing.

Hence I went to research and build a bridge prototype (which they are suppose to do...) to give them something to base on and to benchmark against their miserable effort. Credit of the design goes to Garret Bridges (http://www.garrettsbridges.com/design/trussdesign). So I spent half a day and created this:

Team 2 decided to follow my design with some modifications. It was strong and sturdy but was also very heavy.

Team 1 will use the design based on previous bridge competition that Kranji took part in. The design was very light but the load that it can handle is questionable...

Day 1

Both teams started at 1030 am....

and ended at 430 pm. The 6 hours might sound like a long time but both teams only barely manage to finish on time.

I heaved a huge sigh of relief...

Here the some designs from other schools:

and of course the 2 bridges from Kranji!

Day 2 - Judging

The bridges are loaded at the centre as shown. Loading will stop when the bridge breaks or the maximum load of 30 kg is reached.

In addition, the participants need to explain their design concept to the judges themselves.

Some videos of the loading for our 2 bridges. The jerkiness is due to youtube...:

Team 1

Team 2

Results
Here's a summary of the results of all the bridges at the challenge:


So how did Kranji fare?

Remember, it's not the based on the absolute load but the load factor, which is calculated by the load supported by the bridge divided by the mass of the bridge. E.g. for Team 1, their score is

Team 1 load factor: 10000 / 170 = 58.8

This score actually places them among the top 5! And they went on to win the Merit award!




Team 2 was the highlight of the competition (almost everyone wants to take a look at the Kranji bridge) because it's the only bridge that supported the maximum load of 30 kg. However, they lost in terms of load factor to Pasir Ris Crest which manage to support 16 kg with their bridge that has a mass of only 190 g.... Still, a very good job by Team 2 and they clinched the 2nd place - Silver Award!



Congratulations to all participants! Hopefully you enjoyed and more importantly learned something from this experience. I know I did.... :)