Q&A - PSLE Science

[Robertpattinsonidle]

balu_priya:

Recall those cupcake wrappers? Once it \"open up\", the surface area is much larger than a round cup of similar diameter.


Or perhaps to think about curtains; when the curtain is \"unfolded\", it is about 1.5 times longer.

But the qsn did not say to open up. So anwer should be the first
robertpattinsonidle ft. JB[/quote]
But answer key says its 3.I don't understand.[/quote]
ok...i think i understand wat answer key is saying. the qsn says that metal of same diameter so in math it is true that T has larger exposed surface area when OPENED. but by fact the qsn did not tell to open they just said to leave it like that. so ans should be 1 not 3. u know answer keys are not so correct all the time. thanks
robertpattinsonidle ft.JB

[Robertpattinsonidle]

insanePaPa:

Robertpattinsonidle:

[quote=\"insanePaPa\"]Pls enlighten me, pls.


A plastic beaker, with a hole at the bottom, is held above a waterwheel using a retort stand. Water dripping from the beaker causes the waterwheel to turn. Water drips into a dish place below. State the energy conversion that takes place.

Is this answer correct?
Gravitational potential energy (water in the beaker)--> Kinetic energy (waterwheel)--> Heat & Sound energy (water in the dish).

or this
Gravitational potential energy (water in the beaker)--> Kinetic energy (waterwheel)--> Potential energy (water in the dish).

:thankyou:

insanePaPa

Second one is correct. If possible add sound energy but that is not neede here in this case. Thanks
Robertpattinsonidle ft.JB

Thanks Robertpattinsonidle for your input.
Is it true that if this setup is useful in a particular application (e.g. water turbine to generate electricity), then it should end with 'Potential energy'?[/quote]ok. now the potential energy is the stored energy collected in the dish. and like wat charsen said there is no such thing as water tubine.
thanks
robertpattinsonidle ft.JB

[Robertpattinsonidle]

balu_priya:

Recall those cupcake wrappers? Once it \"open up\", the surface area is much larger than a round cup of similar diameter.


Or perhaps to think about curtains; when the curtain is \"unfolded\", it is about 1.5 times longer.

But the qsn did not say to open up. So anwer should be the first
robertpattinsonidle ft. JB[/quote]
But answer key says its 3.I don't understand.[/quote]
anyways... where did u get this qsn from?

[chow]

Help needed for Henry Park Prelim 2012 Paper 1 Q8. Do you include the "Lime caterpillar" in the population of the "Lime butterfly"? The suggested answer includes.


Thanks in advance!

[kwcllf]

balu_priya:

Recall those cupcake wrappers? Once it \"open up\", the surface area is much larger than a round cup of similar diameter.


Or perhaps to think about curtains; when the curtain is \"unfolded\", it is about 1.5 times longer.

But the qsn did not say to open up. So anwer should be the first
robertpattinsonidle ft. JB[/quote]
But answer key says its 3.I don't understand.[/quote]
3 is correct. As it has many folds, which means surface area is the biggest among all the others (not just the top, but the side folds as well), it should cool fastest.

Imagine those car radiators or aircon compressors, you can find many blades and these blades help to cool the machine down due ti airflow in between these blades or folds.

[charsen]

chow:

Help needed for Henry Park Prelim 2012 Paper 1 Q8. Do you include the \"Lime caterpillar\" in the population of the \"Lime butterfly\"? The suggested answer includes.


Thanks in advance!

Yes.In a population,the young and the adult are included.

[Petkwang]

Can help, not sure whether answer is 2 or 3? Why? http://i47.tinypic.com/15ywx0n.jpg\">

[balu_priya]

Robertpattinsonidle:

balu_priya:

Recall those cupcake wrappers? Once it \"open up\", the surface area is much larger than a round cup of similar diameter.


Or perhaps to think about curtains; when the curtain is \"unfolded\", it is about 1.5 times longer.

But the qsn did not say to open up. So anwer should be the first
robertpattinsonidle ft. JB

But answer key says its 3.I don't understand.[/quote]
anyways... where did u get this qsn from?[/quote]
A school's original prelim paper which has oiginal answers provided by teacher so its definitely correct.

[balu_priya]

kwcllf:

balu_priya:

Recall those cupcake wrappers? Once it \"open up\", the surface area is much larger than a round cup of similar diameter.


Or perhaps to think about curtains; when the curtain is \"unfolded\", it is about 1.5 times longer.

But the qsn did not say to open up. So anwer should be the first
robertpattinsonidle ft. JB

But answer key says its 3.I don't understand.[/quote]
3 is correct. As it has many folds, which means surface area is the biggest among all the others (not just the top, but the side folds as well), it should cool fastest.

Imagine those car radiators or aircon compressors, you can find many blades and these blades help to cool the machine down due ti airflow in between these blades or folds.[/quote]
Your explanation is fantastic. :thankyou: kwcllf and Robert.

[balu_priya]

Please help. My guidebook mentions that balances measure mass not weight http://i50.tinypic.com/9fo5tz.jpg\"> but the given answer is option 3.