Q&A - PSLE Science

[Michaelia0816]

Thx, I kind of bad at this, >.<

[its888me]

ACS 2011 Prelim Paper, Section B, Q41:


http://i49.tinypic.com/2h3btzd.jpg\">
(b) Farmer Amos noticed that his maize plantation has been infested by rats. Without introducing any new species into the above food web, suggest a suitable and sage method that can help him overcome this problem.

Marking Scheme:
- Introduce owls into the community (1)
- Introduce snakes (0)
- Introduce snakes & owls (0)

Why is \"Introduce snakes\" getting a 0 marks since snakes will eat up the rats?

TIA!

[its888me]

its888me:

ACS 2011 Prelim Paper, Section B, Q41:


http://i49.tinypic.com/2h3btzd.jpg\">
(b) Farmer Amos noticed that his maize plantation has been infested by rats. Without introducing any new species into the above food web, suggest a suitable and sage method that can help him overcome this problem.

Marking Scheme:
- Introduce owls into the community (1)
- Introduce snakes (0)
- Introduce snakes & owls (0)

Why is \"Introduce snakes\" getting a 0 marks since snakes will eat up the rats?

TIA!

can someone help?

Many thanks!

[Sun_2010]

its888me:

ACS 2011 Prelim Paper, Section B, Q41:


http://i49.tinypic.com/2h3btzd.jpg\">
(b) Farmer Amos noticed that his maize plantation has been infested by rats. Without introducing any new species into the above food web, suggest a suitable and sage method that can help him overcome this problem.

Marking Scheme:
- Introduce owls into the community (1)
- Introduce snakes (0)
- Introduce snakes & owls (0)

Why is \"Introduce snakes\" getting a 0 marks since snakes will eat up the rats?

TIA!

I think the highlighted word is safe .
That is why cannot be more snakes ?

[charsen]

its888me:

ACS 2011 Prelim Paper, Section B, Q41:


http://i49.tinypic.com/2h3btzd.jpg\">
(b) Farmer Amos noticed that his maize plantation has been infested by rats. Without introducing any new species into the above food web, suggest a suitable and sage method that can help him overcome this problem.

Marking Scheme:
- Introduce owls into the community (1)
- Introduce snakes (0)
- Introduce snakes & owls (0)

Why is \"Introduce snakes\" getting a 0 marks since snakes will eat up the rats?

TIA!

Hi
In my point of view,introducing the snakes would harm other useful animals in the plantation.Not only that,the owl population would also increase,so you can say that both populations would compete for food,which results in the decrease in the number of snakes only.
cheers
Cheers

[elkniwt]

Hi,


Need help on this qn from CHS prelim :

http://i46.tinypic.com/1zp03fb.jpg\">

Answer in answer key is (2). dd's ans is (1) ?? (I think ans key is wrong, need some advices. Thanks!) :?:

[Robertpattinsonidle]

there is only one hole for both water and air to escape. hence the hole is not enough for the air to leave and enter to push the water out. this results in blockage and hence the milk flows out slowly. the second part to this qsn is how to increase flow of milk so u can say that poke another hol and the explanation is that in one hole milk can flow out and in the other air can enter to occupy the space and also push the milk out hence increasing rate of milk flow.

[Chan09]

Need some help as don’t understand why this is false?


When a ball reaches its max height, the force of gravity acting on the ball is the greatest.

Tks

[fightingmom]

Chan09:

Need some help as don't understand why this is false?


When a ball reaches its max height, the force of gravity acting on the ball is the greatest.

Tks

The force of gravity remains the same as it is the same force that pulls everything down to earth. No matter what is the height or weight of an object, the force of gravity will be the same.

NOTE: Don't confuse with gravitational potential energy (GPE) which is affected by height and weight.

Hope it helps.

[Fat Mama]

elkniwt:

Hi,


Need help on this qn from CHS prelim :

http://i46.tinypic.com/1zp03fb.jpg\">

Answer in answer key is (2). dd's ans is (1) ?? (I think ans key is wrong, need some advices. Thanks!) :?:

Hi,

Ans (2) is correct.

Reason being marbles are round and hv gaps bet them. When liquid is pour in, it will fill up the gaps of the marbles. So vol of gas should be more than 700 which is (2) 750