PSLE 2009 - Science

[acelancer]

The question about rod X and the magnet. They put a flame over rod x. what do u guys put? i put lose magnetism and the flame kinetic energy thing(sry can’t remember tht clearly)

[hot_chocolate]

kohjl:

justsay:

As you have mentioned it killed most of the caterpillars but not all. The remaining caterpillars will then multiply and feed of the fruits. So shouldnt it be crop increased and fruit decreased ?

I think catepillars eat leaves and not fruits. Worms eat fruits.
From: kohjl Jr

my answer was that the plant increased and the fruits decreased.

since the caterpillars feed on the plants, when the caterpillars' population decreases, the population of the plants will increase.

however, with less caterpillars, there will be less butterflies to pollinate the flowers of the fruit trees. wouldn't that result in the number of fruits born by the fruit trees decreasing?


that is my reasoning but i'm not sure though. hope someone can confirm it... hope i'm right....

[the ME]

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

My answer was:

Crops-increased
Fruits-decreased

My reason: The pesticides killed most of the caterpillars. Since there are less caterpillars which feed on the plants, the plants increased. When the caterpillars which were the young of the butterfly decreased, the butterflies will also decrease. The butterflies are needed to help the flowers to pollinate. If there are less butterflies to help the plants pollinate, there will be less fruits as a flower can only become a fruit if it goes through pollination. Therefore, there will be lesser fruits.

:?: Am I correct or wrong? :stupid:

[acelancer]

hot_chocolate:

kohjl:

[quote=\"justsay\"]

As you have mentioned it killed most of the caterpillars but not all. The remaining caterpillars will then multiply and feed of the fruits. So shouldnt it be crop increased and fruit decreased ?

I think catepillars eat leaves and not fruits. Worms eat fruits.
From: kohjl Jr

my answer was that the plant increased and the fruits decreased.

since the caterpillars feed on the plants, when the caterpillars' population decreases, the population of the plants will increase.

however, with less caterpillars, there will be less butterflies to pollinate the flowers of the fruit trees. wouldn't that result in the number of fruits born by the fruit trees decreasing?


that is my reasoning but i'm not sure though. hope someone can confirm it... hope i'm right....[/quote]http://pslescience.blogspot.cm has the same ans as u and i think you're right cos' at first i put tht then keng kiang change ans.

[hot_chocolate]

the ME:

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

My answer was:

Crops-increased
Fruits-decreased

My reason: The pesticides killed most of the caterpillars. Since there are less caterpillars which feed on the plants, the plants increased. When the caterpillars which were the young of the butterfly decreased, the butterflies will also decrease. The butterflies are needed to help the flowers to pollinate. If there are less butterflies to help the plants pollinate, there will be less fruits as a flower can only become a fruit if it goes through pollination. Therefore, there will be lesser fruits.

:?: Am I correct or wrong? :stupid:

hey! you have the same answer as me!

[hot_chocolate]

my answer for the lizard and snake question is:


the snake has a larger surface area in contact with the sand than the lizard. thus, there will be more heat transfer to the snake than the lizard.


the lizard moves only on two of its four legs. when it cannot stand the heat on the two legs on which it is traveling, it can always change to the other two legs. however, the snake has only one surface to travel on and cannot change to another surface when it cannot take the heat any longer.


can anyone confirm if my answer is right????

[kohjl]

acelancer:

shinystars:

Hi,

I am a candidate who have just taken the PSLE Science exam. Just wanted to know, what is the correct answer for this question:

Two bulbs are arranged in series. When one bulb is added to the circuit in parallel arrangement, what would happen to the brightness of the first bulb which was arranged in series?

1) It would not light up.
2) It would become brighter.
3) It would become dimmer.
4) It's brightness would remain the same.

Thank you

i put 4.

Please click on the picture at the bottom to see Diagram for a clearer explanation.

I’ve labeled the bulbs as A and B because I can’t remember what letters the examiners had put.

The Question:
Bulb B is shining at a light intensity of 10 units. After pushing the button, bulb B
1) would not light up.
2) would become brighter.
3) would become dimmer.
4) brightness would remain the same.

My answer: 2

My reason: 1 Battery gives 10 units of electricity. After pushing the button, the lever will move up and touch the upper point. As the 3 batteries are now connected with the bulbs, each bulb has 15 units of electricity flowing through them. Since 15 units is more than 10 units, bulb B becomes brighter.

From: kohjl Jr

http://www.postimage.org/image.php?v=Ts159blJ

[acelancer]

kohjl:

acelancer:

[quote=\"shinystars\"]Hi,

I am a candidate who have just taken the PSLE Science exam. Just wanted to know, what is the correct answer for this question:

Two bulbs are arranged in series. When one bulb is added to the circuit in parallel arrangement, what would happen to the brightness of the first bulb which was arranged in series?

1) It would not light up.
2) It would become brighter.
3) It would become dimmer.
4) It's brightness would remain the same.

Thank you

i put 4.

Please click on the picture at the bottom to see Diagram for a clearer explanation.

I’ve labeled the bulbs as A and B because I can’t remember what letters the examiners had put.

The Question:
Bulb B is shining at a light intensity of 10 units. After pushing the button, bulb B
1) would not light up.
2) would become brighter.
3) would become dimmer.
4) brightness would remain the same.

My answer: 2

My reason: 1 Battery gives 10 units of electricity. After pushing the button, the lever will move up and touch the upper point. As the 3 batteries are now connected with the bulbs, each bulb has 15 units of electricity flowing through them. Since 15 units is more than 10 units, bulb B becomes brighter.

From: kohjl Jr

http://www.postimage.org/image.php?v=Ts159blJ[/quote]oh, sry, i don't think it is tht q. for the button spring thing i put your ans

[acelancer]

it is another question:)

[kohjl]

the ME:

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

My answer was:

Crops-increased
Fruits-decreased

My reason: The pesticides killed most of the caterpillars. Since there are less caterpillars which feed on the plants, the plants increased. When the caterpillars which were the young of the butterfly decreased, the butterflies will also decrease. The butterflies are needed to help the flowers to pollinate. If there are less butterflies to help the plants pollinate, there will be less fruits as a flower can only become a fruit if it goes through pollination. Therefore, there will be lesser fruits.

:?: Am I correct or wrong? :stupid:

We cannot assume that the flowers are pollinated by butterflies only.The flowers might be pollinated by other methods such as wind pollination or pollination by bees instead of butterflies.

From kohjl Jr