Q&A - PSLE Science

[Laura02]

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.

I think the question is ambiguous. By definition, gravitational force is the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface; \"the more remote the body the less the gravity\". So gravitational forces are acting in all 3 of the above scenarios (a, b & c). By the question is weather they are \"affected\" by gravitational forces. In a & c, the forces created by \"lift\" is greater than the forces of gravity... I think.

[Laura02]

clblinym:

http://i49.tinypic.com/2mfnion.png\">

Another one is from Rosyth 2001 SA1 Q8.

The answer given is 2. Can anybody explain why? Many thanks. Amy

This is the same principle as why greenhouses work, isn't it?

\"A greenhouse works by taking in sunlight and heating it up. This process is the conversion of solar energy (sunlight) to thermal energy (heat). Greenhouses are designed to allow sunlight to filter through the walls and ceiling. The sunlight warms the trapped air inside, creating chemical reactions. These reactions help the plants to grow to their full capacity while protecting them from outside elements \" quoted from e-how.

[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.