Q&A - PSLE Science

[charsen]

Sunflower 2000:

http://i49.tinypic.com/28s1zro.jpg

Dear Charsen,

Please help to explain the Q30.

Answer Key is 4, however, my DD told me the answer should be 2 since the wheel's rolling direction is D so the frictional force should be B which is opposite to the movment of the wheels.

Thank you very much!

Hi
Well,your daughter is certainly correct.This is a fact.You should memorise this fact which is friction acts on the same direction the wheel moves.If you have a bicycle,dismount the bicycle and observe where friction is produced.

Cheers

[charsen]

Sunflower 2000:

http://i48.tinypic.com/za41t.jpg

Q24 the ansewr key is 4, could you please help to explain the answer. Thanks.

Hi
You know that the starting point of both balls is the same elevation.Therefore,amount of gravitational potential energy converted would be different because of the different slopes,but the ending point is same.Thus,all the energy in the two balls would be converted at the same time to other forms of energy.

You should know that I am a PSLE student.Thus,if i could not answer,inconveineince cause regretted.I am good in science and my niche area is free response.I hope that my explanations are clear to you and to your DD.
With Regards
Charsen

[charsen]

Robertpattinsonidle:

charsen:

Hi Robertpattinsonidle

In the night,both the snails and the water plant would compete for dissolved oxygen.Since this would happen for a month,the snails would eventually die before the water plants die.There would be more dissolved oxygen than dissolved carbon dioxide ,thus the plants would die due to the lack of dissolved oxygen.
Cheers

sorry to disturb again, charsen. why is it that the plants and snails do not die off because of lack of food? isn't that a possible reason too?

Hi
I could not understand your question.Please elaborate your query.
Cheers

[Sunflower 2000]

charsen:

Sunflower 2000:

http://i48.tinypic.com/za41t.jpg

Q24 the ansewr key is 4, could you please help to explain the answer. Thanks.

Hi
You know that the starting point of both balls is the same elevation.Therefore,amount of gravitational potential energy converted would be different because of the different slopes,but the ending point is same.Thus,all the energy in the two balls would be converted at the same time to other forms of energy.

You should know that I am a PSLE student.Thus,if i could not answer,inconveineince cause regretted.I am good in science and my niche area is free response.I hope that my explanations are clear to you and to your DD.
With Regards
Charsen

Dear Charsen,

I have one more question. Why they put a plastic ball and a metal ball? Is it any difference?

Thanks.

[charsen]

Sunflower 2000:

charsen:

[quote=\"Sunflower 2000\"]http://i48.tinypic.com/za41t.jpg

Q24 the ansewr key is 4, could you please help to explain the answer. Thanks.

Hi
You know that the starting point of both balls is the same elevation.Therefore,amount of gravitational potential energy converted would be different because of the different slopes,but the ending point is same.Thus,all the energy in the two balls would be converted at the same time to other forms of energy.

You should know that I am a PSLE student.Thus,if i could not answer,inconveineince cause regretted.I am good in science and my niche area is free response.I hope that my explanations are clear to you and to your DD.
With Regards
Charsen

Dear Charsen,

I have one more question. Why they put a plastic ball and a metal ball? Is it any difference?

Thanks.[/quote]Hi
It is just a distractor to trick you.
Cheers

[fathima]

I cannot do the questions on adaptations , can you post questions more on that particular topic?

[Robertpattinsonidle]

charsen:

Robertpattinsonidle:

[quote=\"charsen\"]Hi Robertpattinsonidle

In the night,both the snails and the water plant would compete for dissolved oxygen.Since this would happen for a month,the snails would eventually die before the water plants die.There would be more dissolved oxygen than dissolved carbon dioxide ,thus the plants would die due to the lack of dissolved oxygen.
Cheers

sorry to disturb again, charsen. why is it that the plants and snails do not die off because of lack of food? isn't that a possible reason too?

Hi
I could not understand your question.Please elaborate your query.
Cheers[/quote]why is it that the snails die off because of lack of air and not die without food?

[Robertpattinsonidle]

charsen:

Hi

Correction.There is no such thing as insulator of heat.This is a wrong usage of scientific words.Remember.Thus,there is only poor conductor of electricity.
Cheers

in my exam, i wrote '' since plastic is a poor conductor of electricity...'' and the teacher marked me wrong for that question. could u explain why? or is my teacher wrong?

[charsen]

Robertpattinsonidle:

charsen:

Hi

Correction.There is no such thing as insulator of heat.This is a wrong usage of scientific words.Remember.Thus,there is only poor conductor of electricity.
Cheers

in my exam, i wrote '' since plastic is a poor conductor of electricity...'' and the teacher marked me wrong for that question. could u explain why? or is my teacher wrong?

Hi
It depends.You could post me the question.I would look at it and explain for you the wrong answer.
Cheers

[charsen]

Hi

The snails do not die because of food,not air.There is sufficient air in the the water.Hence,air is no problem.The snails die because there is no food for them.If they mention that snails eat plants,then the reason would be lack of air.
Cheers