Q&A - P4 Science

[atutor2001]

24by7_mum:

Hi All,


The answer to the qns below is 1. DD and I thinks is none of the answer is correct. LOL both of us are flipping through guide book but none suggested that the answer is 1.

One function of a stem is to
(1) store food for the plant
(2) store oxygen in the plant
(3) take in dissolved mineral salt
(4) hold the plant firmly to the ground

For underground stems such as potato, all the bulbs..., their main function is to store food although their secondary function is to hold the plant firmly to the ground. So in my opinion, both (1) and (4) are applicable.

By the way, most plants do store food in their stems, especially desert plants (cactus).

[usaik]

atutor2001:

Seeds soaked in water will still germinate. Therefore, as long as it has germinated we should not be too concerned with whether the germinated seeds will rot after that since the question did not ask if it will grow into a pla

Noted, thanks for the reply.

[usaik]

Hi,

I need advice on the following question. What should the correct answer be for this following question?
http://i40.tinypic.com/9iwged.jpg\">

The answer given is (4) but doesn't firefly emits \"cold\" light and so C should be wrong? And how do we know that heat is produced when a battery-operated toy is switched on, in what context should we draw this conclusion from.

Appreciate any kind advice on this. Thank you.

[Suz855]

Hi,

Saw this qn in another forum, not convince with the answer, can anyone help, thanks.

John fixed a tube to a balloon and placed it into a basin of water which is half-filled.

1)What will happen to the water level in the basin when air is blown through the tube?
:oops:

[cimman]

usaik:

Hi,

I need advice on the following question. What should the correct answer be for this following question?
http://i40.tinypic.com/9iwged.jpg\">

The answer given is (4) but doesn't firefly emits \"cold\" light and so C should be wrong? And how do we know that heat is produced when a battery-operated toy is switched on, in what context should we draw this conclusion from.

Appreciate any kind advice on this. Thank you.

In general, toys that moves uses electric motors and motors generates heat through friction in the gears and the motor windings. Even if the toy doesn't move, I'm sure there are flashing lights, which also emits heat.
I can't really explain why the firefly emits heat. I've always thought that there's no heat produced from the light of the firefly.
This is another one of those ambiguous questions.

[atutor2001]

usaik:

Hi,

I need advice on the following question. What should the correct answer be for this following question?
http://i40.tinypic.com/9iwged.jpg\">

The answer given is (4) but doesn't firefly emits \"cold\" light and so C should be wrong? And how do we know that heat is produced when a battery-operated toy is switched on, in what context should we draw this conclusion from.

Appreciate any kind advice on this. Thank you.

This should be a P6 question. Only at P6 will energy conversion be taught.

Energy cannot be created nor destroyed. Energy can only be converted from one form to another. All energy forms will ultimately become heat energy.

For the case of the firefly, the energy conversion is as follows:
Chemical potential energy (in the firefly) -> light energy -> heat energy (the emitted light is absorbed by the surrounding and is converted to heat)

[usaik]

Hi atutor2001 and cimman,


Thank you so much for your reply. This question is found in one of the top school p4 paper, the school probably had covered similar question and had taught the children the concept before setting this kind of question for their exam.

[Super.049652kiasu]

Hi All,

Do your have any questions? I am quite good at science.

[mrswongtuition]

Do you mean that the balloon is submerged in the half-filled basin of water?

If yes, then when air is blown into the tube, the balloon fills up with air, pushing the water level in the basin higher. This is due to air in the balloon occupying space and displacing the water.

Regards,
Mrs Wong

[smartmummy]

need help

Study the experimental set-up in the figure below. What will happen to the paper clip after the switch is closed for some time?
http://i43.tinypic.com/34o96bt.jpg\">
1.The paper clip will be attracted to the copper rod.
2. The paper clip will be repelled by the copper rod.
3. The paper clip will rotate about.
4. Nothing will happen.