Q&A - PSLE Science

[balu_priya]

creamyhorror:

balu_priya:

Double-pan balances like that one in the picture actually measure weight. They literally balance the two weights against each other. In space, things are weightless, and the objects would just float without exerting any force on the pans. Thus the beam would remain horizontal (option 3). This is because in space, there's no huge gravitational force pulling the objects down towards the centre of the Earth. That force is what we call \"weight\".

Your guidebook probably says \"balances measure mass\" because the numbers that balances give are in units of mass, e.g. 30kg. But balances are actually measuring weight and providing mass values equivalent to that weight. (edit) Balances will measure mass as long as there is a gravitational force acting on both objects (e.g. when you're on Earth or on another planet). In space there isn't any major gravitational force, so balances won't work properly.

Everything is crystal clear now. :thankyou:

[ximinful]

What causes acid rain? (activities)

[Haneyi]

Ready2WORK:

I agree with VAL82. However, please correct me if I am wrong.

Copper is not a magnetic material, so therefore, magnetic force is able to pass through it. A is therefore correct.
The magnets were attracted towards the copper sheet, which is also towards each other. As unlike poles attract and like poles repel, the unlike poles have to be facing each other. Also, if noted, the question states that after the magnets were released, which means that the original position of the magnets was shown in the diagram, and when released, one of the magnets swiveled around to face the copper sheet which its north pole. D is thus correct.
So, the answer would be (2).

Yes, thank you for the clear explanation, it is very helpful. ^^
Will take note of such tricky questions.

I apologize for the mistake I made, very sorry for giving a wrong answer.

[Clairifina]

To ximinful.

Deforestation
Coal fired power stations
Burning of objects that release poisonous gases
Basically anything that release harmful/poisonous gases causes acid rain.
This is because the poisonous/harmful gases in the air would dissolve in the rain. This would result in acid rain.
Do correct me if I am wrong.

[ximinful]

Clairifina:

To ximinful.

Deforestation
Coal fired power stations
Burning of objects that release poisonous gases
Basically anything that release harmful/poisonous gases causes acid rain.
This is because the poisonous/harmful gases in the air would dissolve in the rain. This would result in acid rain.
Do correct me if I am wrong.

Thanks clairifina

[Clairifina]

You’re welcome.

[paranoid]

charsen:

paranoid:

please help with this question :?: :imdrowning:

http://i48.tinypic.com/2j3ikwi.png\">

Thanks in advance

Ans 1

Option D is not possible as earthworm has a segmented (muti segments) body.

thanks charsen. :thankyou:

[LionelMessi3175]

Robertpattinsonidle:

Too young for old:

Does anyone know the ans to: explain clearly why it is dangerous to throw a stapler out the window from the 10 floor?(scientific ans pls)

there is alot of GPE which converts to alot of KE. thus the impact will be great. may cause death

I agree with robertpattinsonidie the KE from the stapler will cause pressure and pass the energy to the head of the human and may cause a blood clot because of a strong impact.

[cccleo]

Too young for old:

I agree cccleo. Okay, to simplyfie it, the higher it is above mid point, the more gp it has than ke. Vice versa, the lower it is from mid point, the more ke than gp

That means that the opposite points are with same gpe and ke?

[underthesea]

Please help.


1. Which of the following help an aquatic plant to obtain maximum sunlight?

A: Waxy leaves
B: Clasping roots
Swollen leaf stalks
Air spaces in stems

(1) A and C only
(2) B and D only
(3) A, B and C only
(4) A, C and D only

Answer given is (4). How do swollen leaf stalks and air spaces in stems help to obtain more sunlight?

2. Study the energy conversion below.

Chemical Potential Energy -> Kinetic Energy -> Sound + Head Energy

Which of the following action(s) shows the same energy conversion?

A: Clapping of hands
B: Winding up a toy car
Switching on the ceiling fan
Using a hammer to hit a nail

(1) A and D only
(2) B and C only
(3) A, B and D only
(4) A, B, C and D

Answer given is (1). How come winding up a toy car is not correct? DD thinks the answer should be (3).