Q&A - PSLE Science

[G Tan]

bestwishes:

Selfan4ever♥23:

[quote=\"Koky462\"]I have an question on the method of reproduction from my son's exercise.


x - Man, Frog, Polar bear\t\t
y - Yeast, Amoeba, Paramecium
\t
a)What is the main difference between the two methods of reproduction for X & Y?
b)Name the reproduction method under the sub-heading X.

b) External

a) X: Sexual reproduction (involves 2 parents of opposite sexes; involves fertilisation)
Y: Asexual reproduction (involves a single parent; not involve fertilisation)

Frogs in X -- external fertilisation
Mammals in X -- internal fertilisation
Yeast in Y -- budding (a kind of cell division)
Amoeba & Paramecium in Y -- binary fission (a kind of cell division)[/quote]External and internal fertilisation is nt in syllabus anymore

[tinasen]

Thank you!

Sun_2010:

tinasen:

Can anyone help to explain the correct reasoning for this Qn.
The diagram shows an undulating slope. A ball was released from point of the slope. At which point P, Q, R or S , of the slope will the ball have the most gravitational potential energy?
(1) Point P (2) Point Q (3)Point R (4) Point S
The correct answet given in answer key is option (1) where as my DS chose wrongly as (3). http://i42.tinypic.com/35ata8g.jpg\">

The ball will not have the energy to reach PointR since R is at a higher position than P . As such between P and Q, the PE is higher at P

[anneshirleygilbert]

Hello,


I’m having trouble with terminology again! In the topic on Energy, do the terms, "transferred to", "converted into" and "changed to" all mean the same thing? The PSLE guide book uses all 3 terms… will a student be penalized for a ‘wrong choice’ of term, especially in the Open-Ended questions? Please help.

[jesschan]

Hi! Has anyone tried Aitong’s 2011 CA1 MCQs? The answer sheet that I have seems to be full of mistakes. What are your answers to Questions 1,4, 5, 11 & 25?

[Sun_2010]

anneshirleygilbert:

Hello,


I'm having trouble with terminology again! In the topic on Energy, do the terms, \"transferred to\", \"converted into\" and \"changed to\" all mean the same thing? The PSLE guide book uses all 3 terms... will a student be penalized for a 'wrong choice' of term, especially in the Open-Ended questions? Please help.

Let me give this a try
converted into : this refers to different forms of energy. Like kinetic energy of the ball is convert to heat energy, a ball falling down - the PE of the ball is convert to KE of the ball.
Ie same object, or dissipated.

transferred to : refers to energy from one object to another.
Like a you swing a bat and hit a ball. The KE of the bat is transferred to the ball .

Changed - not so specific . We say in general like there will be changes in the energy forms. It could mean both conversion or transfer.

[pixiedust]

Hi all, what's your opinion of statement C - is it true ? and what's the reason ?

Thanks.
(topic : P6 forces)

http://i1197.photobucket.com/albums/aa424/pixie_dust8/ksp2012/sci1.jpg\">

[Nebbermind]

a) true, since a force is needed to push her up.

b) true, since the trampolin will stretch downwards when she land
c) not sure. when she is in contact with the trampolin, her speed would be zero at its lowest point. So definitely it has to increase for her to move up. But once she lose contact with the trampolin, her speed should be decreasing.

Anyone with an alternative explanation?

[mother777]

Hi guys,

I found this beautiful link which explains the energy conversion in different activities via graphics.

It is great to see something and understand. Hope you guys like it

http://www.science-animations.com/support-files/energy.swf

[mother777]

pixiedust:

Hi all, what's your opinion of statement C - is it true ? and what's the reason ?

Thanks.
(topic : P6 forces)

http://i1197.photobucket.com/albums/aa424/pixie_dust8/ksp2012/sci1.jpg\">

Hi,

actually i am bit confused by statement c.
it means the \"speed\" initially increases.
But formula for speed is dist/time.. how to show it is increasing or decreasing here?

wouldn't it be more relevant if the question mentions \" velocity or acceleration\" initially increases?

Because if this was the question, then I will agree to that statement..

what you guys think? and just wonder what the actual answer for this question given in the book?

[pixiedust]

Thanks Nebbermind and mother777 (thanks for sharing the useful link too) !

The answer to the questions stated statements A,B,C are all true ie (4).
However, I have doubts about statement C and trying very hard to relate it to the key concepts in forces.

jesschan:

Hi! Has anyone tried Aitong's 2011 CA1 MCQs? The answer sheet that I have seems to be full of mistakes. What are your answers to Questions 1,4, 5, 11 & 25?

Jesschan, here are my answers, can we discuss to find the right answer ?

Q1 : (1) 5 [different from ans sheet]
Q4 : (1) [same as ans sheet]
Q5 : (3) [same as ans sheet]
Q11: (1) [different from ans sheet]
Q25: (4) [different from ans sheet]

In addition, what is your answer for Q21 ?