Q&A - PSLE Science

[Alchemist]

atutor2001:

vidhyalog:

[quote=\"ms_lim\"]http://i51.tinypic.com/14ah0tl.jpg\">

Ans key : (4), dd's ans : (1)

I agree with your DD's answer. Any others who think differently?

There are 3 variables : material; flame; temperature of water

If both the flame and temperature of water are the same but the pots are of different material, then A is correct i.e. material A is a better conductor of heat which allow faster heat transfer to boil more water using the same time as B.

If both the material and temperature of water are the same but the flame sizes are different, then B is correct i.e. pot B has weaker flame and needs the same time as A to boil less water.

If both the material and flame size are the same but the temperatures of the water are different, then C is wrong because A will take a even longer time because it has more water at lower temperature.

Yes I agree with you.

(I was putting my thoughts into words - that is why so lengthy - hope it is of help to PSLE students on the analysis process)[/quote]Hi atutor,

You have indeed expressed it well. I was trying to convey this to my son moments ago. Will let my son read and see if he can be convinced.

He felt even if A had water of lower temperature, if the B was poor conductor and/or had low flame - that could explain why the time was the same for boiling. So he kept saying, it is possible. Nobody said I must keep the other 2 variables constant. I was trying to argue that he would have used the pricinple of keeping the other 2 variables constant to evaluate Scenarios A and B, so would have to do the same for C. But I had to stop discussing it as he was close to tears.

I hope the PSLE paper will not have too many ambiguous questions.

[P.047330KH]

Hi,

I also think that the ans should be (1), as if the temperature is lower, it will take a longer time to gain heat and then boil(Pot A). However , whoever has set the answer sheet must be thinking that since the flame for Pot A was stronger , it would still boil at the same time . i think that they probably though of this:
Water with lower temperature and exposed to a higher stronger flame will boil at the same time as water with a higher temperature and a weaker flame.
Hope this helps

[atutor2001]

ms_lim:

Please help to explain as don't quite understand this question :

http://i55.tinypic.com/ac3bki.jpg\">
Ans key : (4)

This question is amazing. JC kids doing econ may not know how to solve.

I treat the number of dead plants as the \"cost\" for killing the grasshoppers.

For Brand H
37 dead grasshoppers cost 22 plants
1 dead grass hoppers costs 0.59 plant

For Brand G, 1 dead grass hopper costs 2 plants
For Brand F, 1 dead grass hopper costs 1.21 plants
For Brand E, 1 dead grass hopper costs 2.25 plants

Therefore, we should buy Brand H as it is the \"cheapest\". :rotflmao:

[ms_lim]

atutor2001:

ms_lim:

Please help to explain as don't quite understand this question :

http://i55.tinypic.com/ac3bki.jpg\">
Ans key : (4)

This question is amazing. JC kids doing econ may not know how to solve.

I treat the number of dead plants as the \"cost\" for killing the grasshoppers.

For Brand H
37 dead grasshoppers cost 22 plants
1 dead grass hoppers costs 0.59 plant

For Brand G, 1 dead grass hopper costs 2 plants
For Brand F, 1 dead grass hopper costs 1.21 plants
For Brand E, 1 dead grass hopper costs 2.25 plants

Therefore, we should buy Brand H as it is the \"cheapest\". :rotflmao:

OMG! Is this question out of syllabus? I respect you for being able to come up with such explanation. Thank you.

[ck123]

ms_lim:

http://i56.tinypic.com/vdhft4.jpg\">

Ans key : (2), dd's ans : (3)

Answer should be 3 cause it should repel and not attract with both N

[atutor2001]

vidhyalog:

ms_lim:

http://i55.tinypic.com/10idimx.jpg\">

Ans key : (2), dd's ans : (3)

My son also got (3).

I will pick (2) only if and only if the question is asking for \"most likely\", otherwise, my answer is also (3).

[atutor2001]

vidhyalog:

Could I check the answer for the direction of the frictional force in this question. http://i55.tinypic.com/23u8rhf.jpg\">

For an object that rolls, the frictional force is in the same direction as the motion of the object. (I just asked my kids to remember - some are to young to visualise that the surface of a wheel is rolling backward when the wheel itself is actually moving forward.)

For an object that is being pushed, the frictional force is in the opposite direction of the motion of the object.

[atutor2001]

ms_lim:

http://i51.tinypic.com/20fqp1k.jpg\">

Ans key : (2), dd's ans : (3)

This type of question is very difficult because we must analyse and come out with a conclusion, strictly using only the data given. We must NEVER use any of our personal knowledge!

Case 1 : plastic bowl -> weight & size & material; 15th floor -> height
Case 2 : flower pot -> weight & size & material; 2nd sty -> height
Case 3 : beer bottle -> weight & glass & material
Case 4 : flower pot -> weight & size & material

Therefore, I will say that the data do provide information on weight, size, material and height. However, there is no information on \"hardness\" of each material (don't use your own knowledge).

My answer will than be A (size), B (mass) and D (height).
But there is no A,B,D so the next best one is B,D

(don't get worried that the analysis process is so tedious - it appears tedious only in words. The actual mental process is actually quite fast. Important point to note is \"use only information from the question; no personal knowledge is allowed\")

[r2010]

Red Swastika q 8


Which of the following takes place at Part A (stomach)?

3. Digestive juices and the mixture of food are churned into a thick paste.
4. Digestive juices moisten and totally break down into simpler substances.

The answer key said 3. However, my DS said that it is 4 as the stomach do not turn into a thick paste.


Can someone please help me.
thanks

[Alchemist]

vidhyalog:

Hi - Would appreciate help for this question. http://i52.tinypic.com/2e2mq1x.jpg\">