Q&A - P3 Science

[teh_oh]

tianzhu:

Hi teh_oh


Way of making magnet ----- Stroking

I think stroking is one of the ways of making magnets as described in primary science. It‘s not covered in great details.

I am not too sure if students are required to find out the polarities of magnets produced by single or double stroking method. It may not be in the syllabus. Please check with the school.

Out of curiosity, I checked my boy’s book, Physics Matter.
There is a small topic on “Stroking”
It states “The pole produced at the end of the steel bar where the strokes finish is opposite to the stroking pole used”

You may also read these two interesting sites.

http://www.tutorvista.com/content/physics/physics-i/magnetism/magnetization.php

http://docs.google.com/viewer?a=v&q=cache:VvzUOh8HgLcJ:www.mai-edu.net/LessonFilesDel/Unit%252016%2520-%2520Magnetism.ppt+www.mai-edu.net/LessonFilesDel/Unit+16+-+Magnetism.ppt&hl=en&gl=sg&pid=bl&srcid=ADGEESiPfXZ8w8Onj8rBqh7F3t4iWinNIac3luAVNk0g_XTw5vNX9ZFM2dFJptqk7i1SrrVNvaiy-UuXBvf960Y3B49in-U63yzOMMkL-nbEk3PywYpnnEhSmD8XcWRh5N3DvcFNBao7&sig=AHIEtbRyP1nMuD8kADv4b_QM7n19QyxLNg

For the second site, please refer to page 52 and 53.

Best wishes

Hi Tianzhu,
Thank you too.
For finding out the polarity, my child got it correct. I got thrown off by the wrong answer in the assessment book AND the wrong annotation in the guidebook. Not sure if it is in the syllabus, but such questions came out in two different assessment books that I have.

Thank you again for the information attachments.

[tianzhu]

teh_oh:

Hi Tianzhu,

Thank you too.

Hi

You're welcome.

Best wishes

[rrjan]

Hi, could any of the science gurus here kindly render me some help with this question?


James carried out an experiment by using water and sugar. He placed 2 petri dishes in the same place. He then recorded his observations in the table below at the end of each day.

Petri dish X contains water.
Day 1 - Bacterial growth +
Day 2 - Bacterial growth +
Day 3 - Bacterial growth +

Petri dish Y contains sugar
Day 1 - Bacterial growth +
Day 2 - Bacterial growth ++
Day 3 - Bacterial growth +++

Which one of the 2 substances would you use to speed up bacterial growth? Explain why you have chosen this substance.

My son chose the substance sugar. His explaination is that bacterial likes sugar.

Think this is not the correct way of explaining the reason for his choice, right? How should we state our explaination ?

Any kind help is sincerely appreciated. Thanks

[tianzhu]

Hi


One observes that the difference between set up X and set up Y is that the Petri dish Y contains sugar.

Based on the given data, one can see that the bacteria growth in dish Y is increasing as highlighted by the number of plus signs (+) as compared to dish X which stays the same.

So, one can infer that sugar helps bacteria growth.

I’d choose sugar. The bacteria growth is increasing in dish Y as compared to dish X which remains the same. It shows that sugar speeds up bacterial growth.

Best wishes

[rrjan]

thanks for your kind response, tianzhu

[cimman]

tianzhu:

Hi


One observes that the difference between set up X and set up Y is that the Petri dish Y contains sugar.

Based on the given data, one can see that the bacteria growth in dish Y is increasing as highlighted by the number of plus signs (+) as compared to dish X which stays the same.

So, one can infer that sugar helps bacteria growth.

I’d choose sugar. The bacteria growth is increasing in dish Y as compared to dish X which remains the same. It shows that sugar speeds up bacterial growth.

Best wishes

yes, sugar is a substance that promotes growth in living organisms. It is used primarily used as an energy source. Leaves in plant produces glucose for food, in humans, we burn glucose for energy too.
Of course, too much of glucose and the excess gets stored as fat. So, those with a sweet tooth, lay off the sweets and less fat will accumulate.

[shirley.020816tamzil]

Hi all


Need help with the part b of the below questions
http://i51.tinypic.com/j9n9fk.jpg\">

Answer given by answer sheet was that when the rubber sheet is pulled down, air from the surrounding will draw air through the plastic tube and inflate the balloons.

I don't really understand the answer, can anyone clarify?

[veraclari]

Dear Parents,


Am trying to get my P3 kid interested in Science. Anyone has simple - do at home - experiments to recommend?

I've tried dissolving sugar and Melting of ice, planting seeds. Anything else you can recommend?

Thanks In Advance!!!

[tianzhu]

shirley.tamzil:

I don't really understand the answer, can anyone clarify?

Hi

In answering this question, a student needs to have knowledge of the human respiratory system.

It’s helpful to read your textbook or guidebook(MC) to get some brief notes about the parts and functions of the respiratory system.

The diagram in the question shows the balloon model of a lung in a bottle.
The plastic tube acts as a windpipe and air tubes. The balloons resemble the lungs. The rubber sheet acts as a diaphragm and the inside of the bell jar represents the chest cavity.

When the rubber sheet is pulled downwards, the volume of the inside of the bell jar is increased. This decreases the air pressure inside bell jar so it is lower than the air pressure of the surrounding air. As air flows from a region of higher pressure to a lower pressure region, air flows through the plastic tube into the balloons, thus inflating them.

This is similar in nature when we are breathing in or inhaling.

Hope this helps.

Best wishes

[shirley.020816tamzil]

tianzhu:

shirley.tamzil:

I don't really understand the answer, can anyone clarify?

Hi

In answering this question, a student needs to have knowledge of the human respiratory system.

It’s helpful to read your textbook or guidebook(MC) to get some brief notes about the parts and functions of the respiratory system.

The diagram in the question shows the balloon model of a lung in a bottle.
The plastic tube acts as a windpipe and air tubes. The balloons resemble the lungs. The rubber sheet acts as a diaphragm and the inside of the bell jar represents the chest cavity.

When the rubber sheet is pulled downwards, the volume of the inside of the bell jar is increased. This decreases the air pressure inside bell jar so it is lower than the air pressure of the surrounding air. As air flows from a region of higher pressure to a lower pressure region, air flows through the plastic tube into the balloons, thus inflating them.

This is similar in nature when we are breathing in or inhaling.

Hope this helps.

Best wishes

Thanks for the clear explanation.