PSLE 2009 - Science
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Vikaesh:
Sorry, but i meant if you could find out the answer to the Question. It's alright if you can't. Hope someone else will come forward to help. :lol:[/quote]I'm not very sure but I put something like this:
hey, you cant come up with a good ans after the paper??!! unless you are a tutor or need to publish an assessment book for the coming year? LOL...mew2:
[quote=\"Vikaesh\"] See if you can come up with a good answer for it with the picture. :thankyou: !
http://www.postimage.org/
When the light energy from the torch hits the black and white vanes, the black side of the vanes will convert more light energy into heat energy than the white side of the vanes. Thus the air that is in contact with the black side will expand and push it in the direction.
Is it correct?
From: PlasmaStorm
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Augmum:
Hi Augmum,
hi turquoiseturquoise:
My dd says the diagram is not like the one in the picture too. Her description sounds like your daughter's.
If that is the diagram, then what is the correct answer?
seems that our daughters have alike minds, they both read and see the same thing, for this circuit question and the butterflies question.
your \"that diagram\" isit refers to the one posted?
if yes, then shd be brighter but if the diagram was not drawn like that, then i think the bulb brightness shd remains the same. how i wish i could see the actual diagram!
Yes, they think alike
No, the diagram is not like the one drawn. It's like how your daughter described it, ie the additional parallel bulb is in the middle and connected on the right. -
[quote]Hi Augmum,
Yes, they think alike
No, the diagram is not like the one drawn. It's like how your daughter described it, ie the additional parallel bulb is in the middle and connected on the right.[/quote]Even if the bulb is connected to the right, unfortunately the answer for the bulb in series is still brighter as compared to the other 2 bulbs. My daughter got this wrong. -
mew2:
I remembered that this question used to be very popular in the 90s when my elder kids were taking their PSLE. They need to know convection current then. However, by the time of my last kid (much younger), convection seems to have disappeared from the syllabus.izzit this one?
a diagram of a vane painted with black and white stripes >> with a torch shining on it
what causes the vane to spin?
she attempted the ans this way;
the 'black' portions would absorb more heat relative to the 'white' portions
causing uneven temperature on the surface of the vane
the uneven temperature would cause air current around the surface of the vane, like the zebra cooling effect
the movement of air around the surface cause the vane to rotate...
need to see the diagram if they are vents or black/white stripes though...
right or wrong nvr mind, i think it was a good attempt by her :love:
Anyway, I agree with your girls explanation. She is special because generally girls don't like science. The main key words the question required in the past was : \"hot air rises, pushing the vane\" (if my memory didn't fail me) -
justsay:
Even if the bulb is connected to the right, unfortunately the answer for the bulb in series is still brighter as compared to the other 2 bulbs. My daughter got this wrong.
If the connection of the additional bulb is different, current across the bulbs will definitely be different.
If the additional bulb is added parallel to the existing bulbs in series, according to the configuration drawn by my gal, the current across the bulb is the same. The resistance is the same, voltage is also the same, thus, the bulb brightness remains the same. It all boils down to how the circuit is connected. that's why i am keen to look at the exact configuration. -
kohjl:
The Question:
The farmer found that alot of caterpillars were eating his crops. The farmer sprayed alot of pesticides onto them. Which of the following is correct?
My answer:
Crops-increased
Fruits-increased
Reason: Even if the pesticides kill some of the plants, pesticides will kill most of the caterpillars. Since there are no more caterpillars feeding on the leaves, the number of crops will increase and therefore, the number of fruits will increase.
From: kohjl Jr
No i think it should be veg increase fruit decrease.
Reason:The farmer spray pesticides and kills caterpillars,so less caterpillars will be eating veg so veg will increase.If caterpillar decrease, the number of butterfly will also decrease. So there will be less butterfly to pollinate the fruits,making the fruits decrease
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Hi,i'm a student taking the psle this year.For the snake and lizard question,the first ans. i put same as kojhil's son.For the second ans. i putlegs of lizard hav quite a large surface area so do not sink into sand easily.Can anyone tell me if it's correct or wrog? :?: :?: :?:
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concerned:
Hi,i'm a student taking the psle this year.For the snake and lizard question,the first ans. i put same as kojhil's son.For the second ans. i putlegs of lizard hav quite a large surface area so do not sink into sand easily.Can anyone tell me if it's correct or wrog? :?: :?: :?:
Hi concerned,
The answers are (I think, from what I've heard), the snake's FULL body is on the sand, so there is more friction, slowing it down. The second answer is that less of its body is in contact with the sand so the heat would not get transferred so quickly to it, unlike the snake...
Hope I helped!
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concerned:
Hi,i'm a student taking the psle this year.For the snake and lizard question,the first ans. i put same as kojhil's son.For the second ans. i putlegs of lizard have quite a large surface area so do not sink into sand easily.Can anyone tell me if it's correct or wrog? :?: :?: :?:
Hi concerned,
The answers are (I think, from what I've heard), the snake's FULL body is on the sand, so there is more friction, slowing it down. The second answer is that less of its body is in contact with the sand so the heat would not get transferred so quickly to it, unlike the snake...
Hope I helped!
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