Q&A - PSLE Science

[Pokemonblack]

Hi, I need help with a P6 question.


Due to extensive logging activities in a forest, it causes soil erosion in the area. As a result, large quantity of soil has been washed into the nearby lake during torrential rains.
Based on the above information, which of the following statements about the effect of soil erosion is/are true?

A) The soil particles settle on the bottom of the lake will cause the lake to become increasingly shallow.
B) The amount of dissolved oxygen in the lake will decrease due to the lower rate of photosynthesis of aquatic plants.
C) The population of the fully submerged plants in the murky lake will increase due to increased light availability below the surface.

(1)B only
(2)C only
(3)A and B only
(4)A and C only

Thanks!

[Oldschool]

Pokemonblack:

Hi, I need help with a P6 question.


Due to extensive logging activities in a forest, it causes soil erosion in the area. As a result, large quantity of soil has been washed into the nearby lake during torrential rains.
Based on the above information, which of the following statements about the effect of soil erosion is/are true?

A) The soil particles settle on the bottom of the lake will cause the lake to become increasingly shallow.
B) The amount of dissolved oxygen in the lake will decrease due to the lower rate of photosynthesis of aquatic plants.
C) The population of the fully submerged plants in the murky lake will increase due to increased light availability below the surface.

(1)B only
(2)C only
(3)A and B only
(4)A and C only

Thanks!

Hi,

(3) A and B only.

Soil particle can indeed fill in and destroy wetlands.

Furthermore, suspended soil particles can also block sunlight from reaching plants and algae thus reducing photosynthesis.

As for (C), it contradicts itself.

Regards

[cimman]

atutor2001:

SAHMwith2boys:

Hi all, need help with the following question:


Which of the following objects are not affected by gravitational force?
A. A bird flying in the sky
B. A man lying on the floor
C. A balloon rising into the sky

1. B only
2. A and C only
3. A and B only
4. None of the above

The answer given was (3), but couldn't understand why??

The answer should be (4) because if there is no gravitational force acting on the objects :
A. A bird flying in the sky can stay in the sky without flapping its wings
B. A main lying on the floor can be lifted up with our little finger.
C. A balloon rising into the sky need not be filled with a light gas but can be filled with stone and by give an upward push, it will continue to rise.

another poorly phrased question.
To answer such questions, let's imagine that Earth's gravitational pull increases by 100 times. Will the balloon continue to rise at the same speed, if at all ?

the key hinges on the interpretation of \"not affected\". If one interprets \"not affected\" to mean that the object will continue remain in it's current state regardless of changes in gravitational pull, then (B) would be the answer.
All objects in motion will be affected by changes in gravitational pull. Objects at rest will remain at rest, regardless of gravitational pull, unless it is acted on by an external force. We will have to assume that in a controlled experiment, external forces are not allowed.

[fullhope]

Hi can i know

Is rectum part of large intestine?

Thanks in advance

[PapayaDad]

Answer 3. More ddt more big as ddt accumulates. Small fish have 1 ddt. Big fish eat 5 small fish. Big fish get 5 ddt.

[zinc6539]

fullhope:

Hi can i know

Is rectum part of large intestine?

Thanks in advance

Yes.

[zinc6539]

Goodluck8:

Need help in this question:


The table below shows the level of DDT (an insecticide) found in 4 organisms living in a river.

Organisms DDT Level (parts per million)
A 0.5
B 0.002
C 12
D 2.3

Which one of the following food chains is likely to be formed by these organisms?
(1) A->B->C->D
(2) B->A->D->C
(3) C->D->A->B
(4) D->A->C->B

The answer is 2 or 3? Why?

PapayaDad's explanation is correct. But the answer should be (2) because in a food chain, the arrow points at the consumer/predator.

[fullhope]

Thanks zinc6539 for yr reply.

[dyh]

zinc6539:

clblinym:

http://i49.tinypic.com/14shc9h.jpg\">

This is from RGS 2012 Sa1 Q25
Can anybod here explain why the answer given is 3. TIA. Amy

You can observe from the graph that every 50g increase in weight causes the spring to become 10cm longer. The question also states that the relationship is proportionate until 200g. Therefore:

50g - 20cm
100g - 30cm
150g - 40cm

The total length is 40 cm at 150g. But to find the extension part alone, should minus off the original length which is 10 cm. So i think the answer is 30 cm for the extension alone.

[sembgal]

fullhope:

Hi can i know

Is rectum part of large intestine?

Thanks in advance

Water is absorbed from undigested food in large intestine. Undigested food is stored in the rectum before passing out through the anus.

The large intestine consists of the cecum, rectum and anal canal.

So the answer is YES