PSLE 2012 - Science

[creamyhorror]

AWSP:

But the question is trying to equate stationarity with absence of forces.

Was it? Why do you think so?


I think there are two main ways a P6 student might reason out the answer:

(Shown in diagrams: There is a box on a slope, and a box on a horizontal surface.)

(1) \"Actual friction\" reasoning: The box on the slope is obviously acted on by friction, since gravity is trying to pull it down the slope. However, the box on the surface isn't being pulled or pushed sideways by anything, so it's not being forced into motion. Since friction opposes motion, friction isn't acting on it.

(2) \"Potential friction\" reasoning: Friction occurs whenever surfaces are in contact. Both boxes are in contact with another surface, so friction is acting on them. The box on the horizontal surface can resist someone trying to move it, so that shows that friction is acting on it.

The trouble is that both lines of reasoning can be valid depending on what definition of \"friction is acting\" you go by. I think we all agree that the P6 syllabus doesn't require students to know how to determine if friction is acting on an object.
[quote]My main contention has always been it is extreme testing under the guise of \"application testing\": an unnecessary evil of PSLE.[/quote]I agree with you that the question is inappropriate for P6ers, because answering the question unambiguously relies on them having the next level of knowledge (secondary physics).

I tried checking which of my friends were working in the ST Education desk but it seems most journalists have left...though it would of course be better to approach MOE itself first.

@Sun_2010: Thanks! I'll hang around the forums, if there are interesting things to discuss

[AWSP]

@creamyhorror

In summary, your point on potential friction is the same as my point on stationarity unless the examiner states \"explicitly\" that there is no other forces. But in stating so, he would have crossed over deeper into newtonian physics and static equilibrium concepts.
But that is beside the point, the issue which I am pushing is a broader policy issue in PSLE which merits further attention. The concept grounding is not given and we are trying to test too far out in the content. The result is whether we are looking for \"intuition\" or \"guesswork\". To eliminate the content shortage, additional tuition is often a part of the solution
my 2 cents worth again.

[ultimateschooler]

The word stationarity does not exist. In physics not English.


Newtonian physics is force opposing force which is taught and asked in primary school.

There is no such thing as static equilibrium.  

[ultimateschooler]

The word stationarity does not exist. In physics not English.


Newtonian physics is force opposing force which is taught and asked in primary school.

There is no such thing as static equilibrium.  

[charsen]

Hi

A stationary object has friction,known as static friction.Everybody knows that earth is moving.Therefore,we have friction with the surface we are on so that we do not slip down to the ground.This has been stated in the PSLE revision guide.
cheers

[Rational_Parent]

charsen:

Hi

A stationary object has friction,known as static friction.Everybody knows that earth is moving.Therefore,we have friction with the surface we are on so that we do not slip down to the ground.This has been stated in the PSLE revision guide.
cheers

Charsen, please paste the portion of the PSLE revision guide you are referring to for KSP and interested parties to appreciate, just like Sun_2010 did when we were referred to a document from MIT for our understanding on friction etc.

And here's my two cents worth.......

Everyone should know that gravity keeps all things grounded on earth. Therefore, you do not fall off because of gravity, and unless you drag your feet (i.e. create lateral motion) you will feel and experience friction, and normal force being the weight that you want to exert against the ground you are sliding your feet on.

In other words, there is no frictional force in play until you generate lateral motion with your feet. The amount of frictional force depends on the foot wear you are wearing, and the type of surface your feet is on, and the normal force exerted. Your feet may move restrictively (i.e. kinetic friction at play) or stay put (i.e. normal force unable to overcome static friction).

IMHO, this question seeks to examine the understanding and knowledge of students not just on friction per se but also on the contributing factors (e.g. gravity, normal force, motion, etc) to friction. Science is too diversified a subject and MOE can only set a finite number of questions for students to complete in a fixed time frame. I also do not think MOE wanted to sieve the men from the boys so to speak but it will likely turn out this way if this forum is anything to go by.

Unless there is compelling reasons for me to think otherwise, I am leaning towards what Sun_2010 had convincingly contributed, that there is no friction force when an object is resting on a flat platform.

[verykiasumummy]

oh so many similar as well as different opinions regarding the friction question. so as to say, it should be most likely "ambiguous in the question setting and therefore people made different assumptions". m i right to say that??


i really wonder how the p6 science in another 10yrs time will look like… Pure physics and Pure chemistry?? goodness…

despite all that has been said, no one is 100% sure of the answer, whether it is too much to ask of a p6 or whether they think too much… i guess only the moe knows it themselves… lets move on with it to ensure all other questions are not as ambiguous as this is…

[verykiasumummy]

Bookwrappers:

verykiasumummy:

[quote=\"kwcllf\"]
No wonder you call yourself \"verykiasumummy\"

sorry ya... it is 23 sci guides.... oh my god.... :yikes: :yikes: :yikes:

Wow ksmummy, how to get 22 sci guides in the first plc? Wun u forget n buy 2 of the same?[/quote]hi bookwrappers, i read every single bit of the guide so it is unlikely i cannot remember the content and buy another similar one.... i dun buy them to be displayed nicely in the bookshelf only...

[rains]

Yapyap:

My bother, whose sc teacher saw the answers, says that she said the the answer to the frog/tadpole question is that the tadpoles don't compete with the frogs for food, and if predators eat the frog, they cannot eat the tadpoles.

Eh, you want to bluff also cannot bluff until like that lah. Psle marking hasn't started and the teacher got to see the answers ah? I think even principals also cannot see yet leh.

And tadpoles and frogs eat different types of food. How can competition for food be possible?

Tadpoles eat insects and frogs eat algae or plants ah?

[sammifan]

rains:

Yapyap:

My bother, whose sc teacher saw the answers, says that she said the the answer to the frog/tadpole question is that the tadpoles don't compete with the frogs for food, and if predators eat the frog, they cannot eat the tadpoles.

Eh, you want to bluff also cannot bluff until like that lah. Psle marking hasn't started and the teacher got to see the answers ah? I think even principals also cannot see yet leh.

And tadpoles and frogs eat different types of food. How can competition for food be possible?

Tadpoles eat insects and frogs eat algae or plants ah?

Hello how u know ah? Ppl who wrote that are not bluffing. They can compete for food ok?!?!? U think u marker ah? Pls keep words to urself . ANYWAY, PSLE WAS OVER LIKE A WK AGO SO WHATS THERE TO DISCUSS