Q&A - PSLE Science

[Dharma]

Hi Tianzhu,


For Qn 22, the ball rotates in a clockwise direction towards the boy. Therefore at the point of contact of the ball w/ the ground, the force of motion acts along direction (1). Friction opposes motion, and therefore will act along (3). This is same for wheels of a vehicle moving.

On the other hand, if the ball is replaced with a box that is being pushed towards the boy, the direction of motion of the box is along (3) and the friction acts along (1)

[tianzhu]

Dharma:

Hi Tianzhu,


For Qn 22, the ball rotates in a clockwise direction towards the boy. Therefore at the point of contact of the ball w/ the ground, the force of motion acts along direction (1). Friction opposes motion, and therefore will act along (3). This is same for wheels of a vehicle moving.

On the other hand, if the ball is replaced with a box that is being pushed towards the boy, the direction of motion of the box is along (3) and the friction acts along (1)

Hi, Dharma, you're right.I'll amend the answer.

That's two points in the bag,Thank you for the correction.

But this question touches on rolling friction which may not be in primary science syllabus.

[Drdj]

Dear tianzhu and dharma,


Thanks so much !! Appreciate your detailed explanations !!
Have scanned some further queries from various sources - hope you can help me with them - apologies for the many attachments, as I'm not sure how to do it all in 1 !!
Thanks again
http://www.postimage.org/image.php?v=PqmECgr

http://www.postimage.org/image.php?v=PqmEELA

http://www.postimage.org/image.php?v=PqmEHfJ

http://www.postimage.org/image.php?v=PqmEJKS

http://www.postimage.org/image.php?v=PqmEMf0

[Drdj]

Dear all,


Further queries Thanks in advance
http://www.postimage.org/image.php?v=gx1amC99

http://www.postimage.org/image.php?v=gx1amEEi

http://www.postimage.org/image.php?v=gx1amH8r

http://www.postimage.org/image.php?v=gx1amJDA

http://www.postimage.org/image.php?v=gx1amM7J

[tianzhu]

Hi Drdj


Could you help to provide the sources of your questions eg ACS P6 Sci Q35 SA2 2008?

It appears to me that the questions are from different levels? Just curious, are you a parent or student?

The scanned image may be slightly blurred and small and it may helpful to refer to the originals from http://www.wendykoh.com. Otherwise, it's very taxing for an old man like me to read.

[Dharma]

Drdj:

Dear tianzhu and dharma,


Thanks so much !! Appreciate your detailed explanations !!
Have scanned some further queries from various sources - hope you can help me with them - apologies for the many attachments, as I'm not sure how to do it all in 1 !!
Thanks again

http://www.postimage.org/image.php?v=PqmEELA

Dear Drdj,

Q4) Volume of air will be 500cm3 and 300cm3 in Flask A and B respectively.
Air does not have a definate volume and will spread to occupy the whole container it is in. The capacity of Flask A is 500cm3, so no matter how much air is pumped in, air will compress to occupy the capacity of the flask.

As for flask B, there is 200cm3 of water in it which cannot be compressed. So, air can only occupy the balance 300cm3 space in the flask.

[Dharma]

Drdj:

Dear tianzhu and dharma,


Thanks so much !! Appreciate your detailed explanations !!
Have scanned some further queries from various sources - hope you can help me with them - apologies for the many attachments, as I'm not sure how to do it all in 1 !!
Thanks again

http://www.postimage.org/image.php?v=PqmEHfJ

Air will compress to occupy the max. space in the jar (200cm3)

[Dharma]

Drdj:

Dear tianzhu and dharma,


Thanks so much !! Appreciate your detailed explanations !!
Have scanned some further queries from various sources - hope you can help me with them - apologies for the many attachments, as I'm not sure how to do it all in 1 !!
Thanks again

http://www.postimage.org/image.php?v=PqmEJKS

Q46
a) To find out how different temperatures of water in which the test tube containing yeast with sugar solution is immersed affect the amount of CO2 produced by the yeast.

b) 60 degrees celcius.

c) Sorry, I cant read the Qn

[Dharma]

Drdj:

Dear tianzhu and dharma,


Thanks so much !! Appreciate your detailed explanations !!
Have scanned some further queries from various sources - hope you can help me with them - apologies for the many attachments, as I'm not sure how to do it all in 1 !!
Thanks again

http://www.postimage.org/image.php?v=PqmEMf0

Q8)

I will go for A and C. From the diagram, A looks like ice cubes with water.

If glass contains frozen ice ...NO water (melting has not taken place)...then answer is B and C.

[Dharma]

Drdj:

Dear all,


Further queries Thanks in advance

http://www.postimage.org/image.php?v=gx1amH8r

Hi

Q45b

Length of the day is determined by the time taken by the planet to make 1 rotation on its own axis while 1 revolution is the number of days taken by the planet to revolve round the Sun. There is no relationship between rotation and revolution of the planets.