Q&A - PSLE Science

[stary]

Verysuperkiasu:

stary:

Hi all, need explanation...


A bar magnet, QP, with poles denoted as shown, is suspended in the air. If another magnet, SR, shown in the diagram is brought near P, how would the bar magnet, QP move?

http://www.flickr.com/photos/64113082@N03/6089207068/in/photostream

1) A
2) B
3) C
4) D

Ans: 3

Fact is that the question did not state the poles of the magnet. They might be like poles and then repelled... Why?

Many thanks!

Could there be some missing info on the diagram coz the question states 'with its poles denoted as shown'?

Nope... No info's gone...

[stary]

stary:

Hi all, need explanation...


A bar magnet, QP, with poles denoted as shown, is suspended in the air. If another magnet, SR, shown in the diagram is brought near P, how would the bar magnet, QP move?

http://www.flickr.com/photos/64113082@N03/6089207068/in/photostream

1) A
2) B
3) C
4) D

Ans: 3

Fact is that the question did not state the poles of the magnet. They might be like poles and then repelled... Why?

Many thanks!

Question is from (MGS/CA1/2009/Primary 5/Qns 1)

[Verysuperkiasu]

Nebbermind:

FOOD?!

Yah hor, forgot abt the animals' food part. but plants will survive coz they can make their own food right? But I need to know :

1) option 2 says 'plants will survive longer than larger animals'. Why only larger animals?

2) Assuming food is given to the animals, then can the answer be (4) - will this constant exchange of gases between the plants and the animals be able to last for several months?

Thanks

[Sun_2010]

stary,


It will move in the direction of C
Nebbermind had given the reason above.

[stary]

Thanks guys for the prompt reply!

[stary]

Hi all, need explanation again.


Refer to (SCGS/Prelim/P6/2010/Booklet B/Question 40)

Samantha put up the 3 set-ups below. All the set-ups had similar plants and 250ml of water each but differnt humidity levels. She conducted the experiment for 3 days. She wanted to find out if humidity level affects the amount of water lost by the plant through its stomata.

Set-up A (Humidity: 90%)
Set-up B (Humidity: 29%)
Set-up C (Humidity: 57%)


...........

a)What......... plants through its stomata?
My answer: The higher the humidity level, the lesser the amount of water lost by the plants through its stomata.
Ans sheet: The higher the humidity level, the more the amount of water lost by the plants through its stomata.

Many thanks!

[mother777]

stary:

Hi all, need explanation again.


Refer to (SCGS/Prelim/P6/2010/Booklet B/Question 40)

Samantha put up the 3 set-ups below. All the set-ups had similar plants and 250ml of water each but differnt humidity levels. She conducted the experiment for 3 days. She wanted to find out if humidity level affects the amount of water lost by the plant through its stomata.

Set-up A (Humidity: 90%)
Set-up B (Humidity: 29%)
Set-up C (Humidity: 57%)


...........

a)What......... plants through its stomata?
My answer: The higher the humidity level, the lesser the amount of water lost by the plants through its stomata.
Ans sheet: The higher the humidity level, the more the amount of water lost by the plants through its stomata.

Many thanks!

Hi Stary,

I agree with your answer too.

Just to confirm again, I searched the internet and found the below explanation:

\" Relative humidity: As the relative humidity of the air surrounding the plant rises the transpiration rate falls. It is easier for water to evaporate into dryer air than into more saturated air.\"

This is from the link below.
http://ga.water.usgs.gov/edu/watercycletranspiration.html

This link also explain other factors affecting plant transpiration.

Hope this helps (lets also wait for other KS parents to reply back too and enlighten us)

[stary]

Thanks mother777!

[Ash001]

Need help here. School answer is 4

My son answer is 1

I had asked my son to asked the teacher.
-Her explanation is diagram C is with same brightness. I am not convinced here. Look at the qns once again, the keyword is \"light up\" with \"equal brightness\"

-I dont really know the explanation on diagram D as my son didnt understand what she was saying. This diagram D confirm only the upper bulk get light up.



http://i56.tinypic.com/bdwjv8.jpg\">

[tianzhu]

Verysuperkiasu:

But I need to know :


1) option 2 says 'plants will survive longer than larger animals'. Why only larger animals?

2) Assuming food is given to the animals, then can the answer be (4) - will this constant exchange of gases between the plants and the animals be able to last for several months?

Hi Verysuperkiasu

We can apply the concepts behind the terrarium to answer your question.

Here’s a link to a write up which offers good explanation on how air is recycled in a terrarium.

http://www.ehow.com/info_8739797_do-terrariums-recycle-air.html

Going through the elimination process in the MCQ’s choices, we can immediately rule out (1) and (3).

On closer examination, (4) is also out as organisms need more than air to survive. As taught in lower primary science, living things need air, food and water to stay alive.

This leaves us with (2) which is the answer to the MCQ question.

Usually the animals and plants are carefully selected to live in an enclosed container, one doesn’t pick animals which would fight and eat other animals or cause destruction to the plants.

I guess a logical explanation is that a bigger animal(assuming non plant eater) has a bigger body and with that a bigger appetite, hence their chances of survival decreases when food becomes scarce.

As to your second question on the limit for recycled air, please refer to the last paragraph(brief history) of the article.

Hope this helps.

Best wishes