Q&A - PSLE Science

[Zhu99]

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

The correct answer is 4.

Question asks for frictional force (air resistance) acting on the man and the gavitational force acting on bicycle.

[Robertpattinsonidle]

charsen:

Robertpattinsonidle:

[quote=\"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[/quote]this question part b. http://i49.tinypic.com/nl4imt.jpg\"> http://i47.tinypic.com/2i23n82.jpg\">

[Winx5015]

http://i49.tinypic.com/293u6hg.jpg\">


How to answer (a) ? :imdrowning:

Thanks:)

[Robertpattinsonidle]

Winx5015:

http://i49.tinypic.com/293u6hg.jpg\">


How to answer (a) ? :imdrowning:

Thanks:)

One is. Length of string that is in betwewn the bridge and the weight. The more the string the lesser the gravitational pull so it is a important variable that must be kept constant. The material used for the bridge must also be same. Metal can hold more weight than wool for example

[Zhu99]

charsen:

Robertpattinsonidle:

[quote=\"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.

this question part b. http://i49.tinypic.com/nl4imt.jpg\"> http://i47.tinypic.com/2i23n82.jpg\">[/quote]
b. Property -- Objects E and G do not allow electricity to pass through.

[Winx5015]

Thanks Robertpattinsonidle for your help

[Zhu99]

Winx5015:

http://i49.tinypic.com/293u6hg.jpg\">


How to answer (a) ? :imdrowning:

Thanks:)

a i. The place the experiments is conducted.

a ii. The distance of the string from the each desk.


b. The weights when the bridge just collapsed. The greatest reading (weight) is the one with the strongest beam.

[charsen]

Hi robertpattinsonidole,

Your teacher is wrong.I would confirm with you tomorrow.My teacher would not accept insulator of electricity.Plastic can conduct lightning,which is a fact.Therefore,there is no such thing as insulator of electricity.
Cheers

[Sunflower 2000]

Zhu99:

charsen:

[quote=\"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

The correct answer is 4.

Question asks for frictional force (air resistance) acting on the man and the gavitational force acting on bicycle.[/quote]Thank you very much! :udaman:

[charsen]

Zhu99:

Winx5015:

http://i49.tinypic.com/293u6hg.jpg\">


How to answer (a) ? :imdrowning:

Thanks:)

a i. The place the experiments is conducted.

a ii. The distance of the string from the each desk.


b. The weights when the bridge just collapsed. The greatest reading (weight) is the one with the strongest beam.

Hi
The place differs the size of the beam.But the mass remains the same when the beam expands or contracts.Another alternative is the type of string must be the same.
Cheers