Q&A - P4 Science

[smartmummy]

:thankyou:

teh_oh:

serenasgreenhouse:

[quote=\"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.

Hi, smartymummy.

Answer is 4.

Explanation:
Copper is non-magnetic. Hence the copper rod cannot become an electromagnet to attract the clip.

Hi,
Agree that copper is not a magnetic material, hence cannot be magnetized to attract the clip.[/quote]

[smartmummy]

1) a tricky qn indeed, theory tells that the air can spread out take up the space of the container can hold

2)300cm3
May expert help u further

teh_oh:

smartmummy:

These type of qns, how much capacity the container can hold is the volume of air. Doesn't matter how much we pumped into the container.
1)300cm3
2) didn't mention the sealed flask's capacity?[quote=\"teh_oh\"]Dear parents,

Appreciate your help in the following two questions regarding Matter.

Air occupies space and has indefinite volume, hence it takes up the shape of its container (indefinite shape)

Question 1: 100cm3 of air is pumped into a flattened football which can hold up to a capacity of 300cm3. How much air is inside the football after the air is pumped into it?

Question 2: 100cm3 of air is pumped into a sealed flask which has vacuum inside. How much air is inside the flask after the air is pumped into it?

Thank you. I do not have any answers as these questions were posted to me by my child.

Hi smartmummy,

1. If after pumping in 100cm3 of air into the flattened football and the resultant air volume inside the football is 300cm3, then does it mean that a flattened football with 200cm3 of air pumped into it will result in 300cm3 air volume inside the football? if yes, how to explain that the pumped-up football will then have different 'firmness' due to the different amount of air injected into it?

2. Sorry. The sealed flask capacity is 300cm3.
Question 2: 100cm3 of air is pumped into a sealed flask capacity of 300cm3 which has vacuum inside. How much air is inside the flask after the air is pumped into it?

Thank you.[/quote]

[Nebbermind]

I believe for the flattened football, the air inside will try to achieve the same pressure as the outside. So if the air when outside the ball is 100cm3, it’ll occupy 100cm3 inside the ball. This will be true up to 300cm3.

[teh_oh]

Nebbermind:

I believe for the flattened football, the air inside will try to achieve the same pressure as the outside. So if the air when outside the ball is 100cm3, it'll occupy 100cm3 inside the ball. This will be true up to 300cm3.

Hi Nebbermind,
Thanks.
I suspect that the flattened football will behave like a balloon too regardless of the capacity it can hold. Now want to see if any other comments on this.

Do you have any answer for my Question 2 regarding the flask with vacuum inside (not sure if my question is realistic).

Thanks.

[Nebbermind]

The diff is that the ball does not have a fix volume until it’s fully inflated (300cm3), ie, it can go from 0cm3 (flattened) to 300cm3 (fully inflated).


For the flask, it has a fixed volume inside. So whatevere amt of air pumped in will have only 1 volume. Even the vacuum before the air pumped in is 300cm3, ya?

[teh_oh]

Thanks Nebbermind for your explanation.

[smartmummy]

can anyone explain me the reason of the following please.


When we bring the bar magnet near to the compass.compass show the direction according to the bar magnet.What is the reason? http://i41.tinypic.com/351775s.jpg\">

[jedamum]

The needle of the compass is a small magnet by itself.

[youngtay]

need help for the following, how to draw 2 light rays for q 19c?


Thanks http://i42.tinypic.com/2hye0w4.jpg\">

[smartmummy]

jedamum:

The needle of the compass is a small magnet by itself.

thanks jedamum!