Tutor Niedino: Pri Science Questions and Concepts

[Niedino]

Dear Parents


I have just posted some tips on my blog on how to answer Section B questions. Unfortunately, its not been posted on the main page yet. Here's the link. http://www.kiasuparents.com/kiasu/conte ... -questions

Here's my tutor profile on kiasuparents which has been verified by ChiefKiasu. http://www.kiasuparents.com/kiasu/conte ... ng-niedino

I have helped many pupils to improve in their Science during this year's PSLE.

I have some classes opening in 2012, if you and other parents are interested, you may want to drop me an email at [email protected] or pm me for my contact details.

You may also wish to join my mailing list (which I'll start once there are enough interested parents).

Hope it helps

Niedino

[Pebblesrock]

Why does the electrostatic force of attraction decreases when the size of the ion decreases whereas when the molecules get bigger in a covalent compound, the intermolecular force of attraction increases? It sounds contradicting.

[petals73]

Hi I would like to find out more on the marking scheme for PSLE science.


My P4 DD had these type of questions during her SA1 and CA2 exams. One of them were:
They were given 7 things and were told to group them into "good" and "bad" conductors of heat. The correct answer will be 3 items will fall into "good" and 4 items will fall into "bad". She’s got 5/7 correct but no marks were awarded at all. So she lost the entire 2 marks. When I checked with her teacher, she said the school were following the marking scheme of PSLE.

Please advise if this is true. Many thanks

[Niedino]

Goodluck8:

Need help


When DDT is used, will the conentration of the DDT level in the food consumers be higher or lower? The school teacher explained that it will be lower as DDT will be expelled from the animals through their faeces. DDt will only kill the insects but not the animals

But i read quite a number of articles and seem it is not true. Can you help me?thanks

Second question
which requires more force : pulling the load up a inclined plane or lifting the same load vertically up? The teacher answer is pulling it up a inclined plane because it need to overcome gravity and frictional force but lifting it up requires to overcome the gravity only.????

Dear Goodluck,

Apologies for the late reply. Its really been busy. For the first question, I believe that it depends on the amount of DDT. Without the question, I am unable to comment more.

As for the second question, the accepted answer is usually the inclined plane as 2 forces need to be overcome instead of 1. However, if there is a way to reduce the frictional force, e.g. adding wheels, or adding lubricants, then it may be different. I can see where the child must be thinking, if I cannot lift this, perhaps I can push it along the ground. But pushing it up a ramp and pushing it along a flat ground requires a different amount of force.

Hope it helps!

[Nebbermind]

Goodluck, is the force qyestion for p6 and is it from school or enrichment centre?

[mwchua]

hi Niedino, dropped you a pm…just wondering if you have have chance to read through yet? thanks.

[phtthp]

Hi niedino,

I had sent u a pm. Appreciate if u can respond. Tq

[Nebbermind]

For the force qn, since you to need forces, one to move forward n another to move upwards, to move the load up an inclined plane, the resultant force will be greatest among the lot.


As for the DDT qn, the scavenger which feed on the dead insects will have the highest level. Those that eat the scavenger will have lower and so on.

Correct me if I’m wrong.

[Sun_2010]

Goodluck8:

Need help


When DDT is used, will the conentration of the DDT level in the food consumers be higher or lower? The school teacher explained that it will be lower as DDT will be expelled from the animals through their faeces. DDt will only kill the insects but not the animals

But i read quite a number of articles and seem it is not true. Can you help me?thanks

Second question
which requires more force : pulling the load up a inclined plane or lifting the same load vertically up? The teacher answer is pulling it up a inclined plane because it need to overcome gravity and frictional force but lifting it up requires to overcome the gravity only.????

for the force question , the inclined plane is incorrect.
In fact inclined plane is a simple machine. It is definitely easier to push things up a slope than lift it.

Yes while pulling a load up the slope we over come friction and gravity. However the force to overcome gravity is lesser as it is only a component of the mass x g.

Unless the inclined plane has extremely high friction in comparison to the weight of the load. But this has to be specifically mentioned as is practically not the case .

[Nebbermind]

Sun_2010:

for the force question , the inclined plane is incorrect.
In fact inclined plane is a simple machine. It is definitely easier to push things up a slope than lift it.

Yes while pulling a load up the slope we over come friction and gravity. However the force to overcome gravity is lesser as it is only a component of the mass x g.

Unless the inclined plane has extremely high friction in comparison to the weight of the load. But this has to be specifically mentioned as is practically not the case .

You are right!

I should have sketched the diag before my above answer :oops: