Q&A - PSLE Science

[kwcllf]

its888me:

Nan Hua Prelim 2011, Q37.


Meilin wants to carry out a fair test to find out which type of soil, P, Q or R allows the most water to pass trhough.

The table below shows the results of her experiments.

(c) Based on the data in the result table, which type of soil is most suitable for a plant that grows well in a dry and sandy habitat? Give a reason, for your answer.

http://i45.tinypic.com/mmpu11.jpg\">

Answer provided is : Sample Q. It allows the most water to flow througho in the given time and means that it does not retain water well and hence is best for plants that grow well in a dry habitate which do not need a lot of water.



However, my child said he that he is going crazy now as previously he did a similar question which a different answer. Thus, he is very confused now but can't find the previous question that he did. Anyway, the previous answer was something like the following:

Sample P. It does not allow a lot of water to pass through, so the plant can take in the water quickly.

Please help urgently as prelim is tomorrow.

TIA!

If it is a dry and sandy habitat, then water can easily pass through. So the answer P and the reasoning you gave above is not correct. Therefore, answer should be Q as water can easily flow through the soil medium.

[elkniwt]

Hello,


Pls help.

What is the energy conversion for \"switching on the ceiling fan? :?:

Thanks in advance.

[charsen]

elkniwt:

Hello,


Pls help.

What is the energy conversion for \"switching on the ceiling fan? :?:

Thanks in advance.

Hi
(ANS)Electrical energy---->Kinetic Energy+heat energy+sound energy

The electrical energy in the main sockets converts into kinetic energy when you turn on the ceiling fan as the motor in the ceiling fan is moving.Heat energy is produced between the motor and the blades of the fan.You would hear sounds from the fan won't you?Hence,this shows that sound energy is produced.
Hope this explanation works.
Cheers

[charsen]

its888me:

Nan Hua Prelim 2011, Q37.


Meilin wants to carry out a fair test to find out which type of soil, P, Q or R allows the most water to pass trhough.

The table below shows the results of her experiments.

(c) Based on the data in the result table, which type of soil is most suitable for a plant that grows well in a dry and sandy habitat? Give a reason, for your answer.

http://i45.tinypic.com/mmpu11.jpg\">

Answer provided is : Sample Q. It allows the most water to flow through in the given time and means that it does not retain water well and hence is best for plants that grow well in a dry habitate which do not need a lot of water.



However, my child said he that he is going crazy now as previously he did a similar question which a different answer. Thus, he is very confused now but can't find the previous question that he did. Anyway, the previous answer was something like the following:

Sample P. It does not allow a lot of water to pass through, so the plant can take in the water quickly.

Please help urgently as prelim is tomorrow.

TIA!

Hi
Facts you should know:Sandy soil has large with many air spaces in between.Thus,it does not hold water well and has a good amount of air inside the soil.
Hence,soil sample Q probably has large air spaces in between.Therefore,very few plants can grow in sandy soil,as the amount of water in the soil is enough for them to support their growth.
Cheers

[enreachlearningcentre]

[quote]Chan09 wrote:

Need some help as don't understand why this is false?

When a ball reaches its max height, the force of gravity acting on the ball is the greatest.

Tks[/quote]Hi, this qn relates to the principle of conservation of energy.
Consider a ball being thrown upwards, the total energy is simply the sum of Grav. Potential Energy(GPE) + Kinetic Energy(KE)= constant
GPE depends on mass & height. KE depends on mass & velocity.
As ball goes up higher, KE is being converted to GPE in order that total energy is a constant.
So at max height, KE is zero(as ball's velocity is zero at that instant) giving GPE to be greatest.
This max GPE is the result of max grav. force acting on the force.

Hope it helps

[kitty2]

Please help with these questions :?: :thankyou:


1)There's a herd of elephants.How do they adapt to escape from their predators?Explain why this method of adaptation is effective?

2)Describe the typical habitat of a polar bear.How is the polar bear adapted for surviving in its habitat?List 3 ways.

3) Describe the typical habitat of a grizzly bear.The grizzly bear and the polar bear are both adapted to survive in a cold enviroment.What is the difference between the climate conditions of the grizzly bears' habitat and the polar bear's habitat?

4) How is grizzly bear adapted to survive in its habitat.List 2 ways.

5) Apart from the grizzly bear,name another animal that has a similar behavioural adaptation.

[elkniwt]

Hi charsen,


Thank you very much!!! I like your explanation. Very clear.
:thankyou:

My dd is asking if the question is referring the energy conversion for the action of turning on the fan ???

Chemical Potential Energy (your body) -> Kinetic energy (the action turning on switch) -> then we don't know already ??

charsen:

elkniwt:

Hello,

Pls help.

What is the energy conversion for \"switching on the ceiling fan? :?:

Thanks in advance.

Hi
(ANS)Electrical energy---->Kinetic Energy+heat energy+sound energy

The electrical energy in the main sockets converts into kinetic energy when you turn on the ceiling fan as the motor in the ceiling fan is moving.Heat energy is produced between the motor and the blades of the fan.You would hear sounds from the fan won't you?Hence,this shows that sound energy is produced.
Hope this explanation works.
Cheers

[Robertpattinsonidle]

elkniwt:

Hi charsen,


Thank you very much!!! I like your explanation. Very clear.
:thankyou:

My dd is asking if the question is referring the energy conversion for the action of turning on the fan ???

Chemical Potential Energy (your body) -> Kinetic energy (the action turning on switch) -> then we don't know already ??

charsen:

[quote=\"elkniwt\"]Hello,

Pls help.

What is the energy conversion for \"switching on the ceiling fan? :?:

Thanks in advance.

Hi
(ANS)Electrical energy---->Kinetic Energy+heat energy+sound energy

The electrical energy in the main sockets converts into kinetic energy when you turn on the ceiling fan as the motor in the ceiling fan is moving.Heat energy is produced between the motor and the blades of the fan.You would hear sounds from the fan won't you?Hence,this shows that sound energy is produced.
Hope this explanation works.
Cheers

[/quote]if the fan is the battery operated one, then it is:
chemical potential energy to electrical energy to kinetic energy+ sound energy+ heat energy
chemical potential in our body does not count if they are talking about energy conversion in fan and not from when we switch the fan on. anyways, the chemical potential energy does not transfer to the kinetic energy in the switch's movement. it starts only from electricity in the close circuit

[Alarmchain]

Hi elkniwt,


This is yet another excellent example of an ambiquous question.

Especially for this topic of energy conversion, my DD often gets confused as to what degree of details is expected? In this instance, is it Chemical Potential Energy of Body = KE of finger + KE of switch + Sound Energy? Or is it as pointed out by Charsen?

I would think it is the latter, but in expecting the children to be detailed and specific with their answers, I have often seen questions which are NOT specific and detailed to begin with … sigh …

In my effort to help my DD maintain her interest and, more importantly, her confidence in her reasoning skills, I will listen to her logic behind her explanation and if it makes sense, I will reassure her to ignore the marks and explain why I think her answer is right or wrong.

No choice, would rather lose this battle than the war for knowledge.

Cheers!

[Robertpattinsonidle]

Alarmchain:

Hi elkniwt,


This is yet another excellent example of an ambiquous question.

Especially for this topic of energy conversion, my DD often gets confused as to what degree of details is expected? In this instance, is it Chemical Potential Energy of Body = KE of finger + KE of switch + Sound Energy? Or is it as pointed out by Charsen?

I would think it is the latter, but in expecting the children to be detailed and specific with their answers, I have often seen questions which are NOT specific and detailed to begin with .... sigh .....

In my effort to help my DD maintain her interest and, more importantly, her confidence in her reasoning skills, I will listen to her logic behind her explanation and if it makes sense, I will reassure her to ignore the marks and explain why I think her answer is right or wrong.

No choice, would rather lose this battle than the war for knowledge.

Cheers!

for what my teacher told me[i am currently a psle student], my teacher said to answer the question directly; in a way that we are actually in a straight forward manner and what is accepted
in this cas, what we need to say is this:
electric energy in the complete circuit when switched on converts to kinetic energy when the fan spins + unwanted energy when the fan spins, such as heat+sound energy.
this is it, according to my teacher.
in specific qsns it will be stated :'explain what will happen in energy conversion from the moment that the john's hand touches the switch.as
i said before, chemical potential energy in john's hand does not change to electric energy in circuit because john's hand is giving a force and not an energy.

cheers! :imcool: