PSLE 2012 - Science

[Sun_2010]

AWSP:

The precise answer is :

a) whether there is any friction or not depends on whether there is any force applied on the object or not and the direction that it is applied. If on the slope, a force is applied such that there is a component of the same magnitude that is opposite and equal to the vector force due to gravitational force, the frictional force will be zero as well.
b) likewise if there is any force applied such that a net horizontal resultant vector force exist on the object on the horizontal surface, there is friction (whether it moves or not).
I dont think all these are spelt out clearly in the question. The setter did not specify the forces applied and he could also not specify because even if he did, in order to comprehend the full implication, the student need to know how to vectorise the forces and newton's 1st and 3rd law.
This is an extreme case of a setter who is trying to test for \"intuition\" but does not have sufficient knowledge to set the context properly.
In my opinion, it is an \"illegal\" question and we should challenge it with MOE.

Beg to differ. If there is no mention of any external force in the question or the diagram, it just means there is no such external force acting on the object. The only force that is assumed in such cases is that due to gravity.

While P6 students donot need to know about components of force.and stuff, it should be common sense that to move an object down a slope is easier than that required to move it on a horizontal surface. And that is because of gravity aiding it. And that gravity does not help in moving an object horizontally. What I mean by that- if I want to push an object horizontally then I could push (exert a force) horizontally, or even at an acute angle. But if I were to push it down no matter how hard, still it would not move at all.

Friction is said to be the force that opposes motion. This is taught in the syllabus.

IMHO, children a keen interest for physical sciences are likely to conclude this. There are children who think about why when they play be it down the slide ( the higher the inclination, faster they slide, the longer the slide the greater the speed they hit the ground ) , with tops, ball games, carroms , science is aplenty. Being able to associate that with what you have read is what makes scientific thinking.
Again, IMO,
Is this a toughie , yes sure. Probably one of the differentiating Qs
Is it wrongly set , no I think, it is brilliantly set.

[sleepyqueen]

Sun_2010:

AWSP:

The precise answer is :

a) whether there is any friction or not depends on whether there is any force applied on the object or not and the direction that it is applied. If on the slope, a force is applied such that there is a component of the same magnitude that is opposite and equal to the vector force due to gravitational force, the frictional force will be zero as well.
b) likewise if there is any force applied such that a net horizontal resultant vector force exist on the object on the horizontal surface, there is friction (whether it moves or not).
I dont think all these are spelt out clearly in the question. The setter did not specify the forces applied and he could also not specify because even if he did, in order to comprehend the full implication, the student need to know how to vectorise the forces and newton's 1st and 3rd law.
This is an extreme case of a setter who is trying to test for \"intuition\" but does not have sufficient knowledge to set the context properly.
In my opinion, it is an \"illegal\" question and we should challenge it with MOE.

Beg to differ. If there is no mention of any external force in the question or the diagram, it just means there is no such external force acting on the object. The only force that is assumed in such cases is that due to gravity.

While P6 students donot need to know about components of force.and stuff, it should be common sense that to move an object down a slope is easier than that required to move it on a horizontal surface. And that is because of gravity aiding it. And that gravity does not help in moving an object horizontally. What I mean by that- if I want to push an object horizontally then I could push (exert a force) horizontally, or even at an acute angle. But if I were to push it down no matter how hard, still it would not move at all.

Friction is said to be the force that opposes motion. This is taught in the syllabus.

IMHO, children a keen interest for physical sciences are likely to conclude this. There are children who think about why when they play be it down the slide ( the higher the inclination, faster they slide, the longer the slide the greater the speed they hit the ground ) , with tops, ball games, carroms , science is aplenty. Being able to associate that with what you have read is what makes scientific thinking.
Again, IMO,
Is this a toughie , yes sure. Probably one of the differentiating Qs
Is it wrongly set , no I think, it is brilliantly set.

Oh mine the answer seems long. My DS would just give a short and sweet answer to it as usual. hmm..like that how to score?!?

[AWSP]

Sun_2010:

AWSP:

The precise answer is :

a) whether there is any friction or not depends on whether there is any force applied on the object or not and the direction that it is applied. If on the slope, a force is applied such that there is a component of the same magnitude that is opposite and equal to the vector force due to gravitational force, the frictional force will be zero as well.
b) likewise if there is any force applied such that a net horizontal resultant vector force exist on the object on the horizontal surface, there is friction (whether it moves or not).
I dont think all these are spelt out clearly in the question. The setter did not specify the forces applied and he could also not specify because even if he did, in order to comprehend the full implication, the student need to know how to vectorise the forces and newton's 1st and 3rd law.
This is an extreme case of a setter who is trying to test for \"intuition\" but does not have sufficient knowledge to set the context properly.
In my opinion, it is an \"illegal\" question and we should challenge it with MOE.

Beg to differ. If there is no mention of any external force in the question or the diagram, it just means there is no such external force acting on the object. The only force that is assumed in such cases is that due to gravity.

While P6 students donot need to know about components of force.and stuff, it should be common sense that to move an object down a slope is easier than that required to move it on a horizontal surface. And that is because of gravity aiding it. And that gravity does not help in moving an object horizontally. What I mean by that- if I want to push an object horizontally then I could push (exert a force) horizontally, or even at an acute angle. But if I were to push it down no matter how hard, still it would not move at all.

Friction is said to be the force that opposes motion. This is taught in the syllabus.

IMHO, children a keen interest for physical sciences are likely to conclude this. There are children who think about why when they play be it down the slide ( the higher the inclination, faster they slide, the longer the slide the greater the speed they hit the ground ) , with tops, ball games, carroms , science is aplenty. Being able to associate that with what you have read is what makes scientific thinking.
Again, IMO,
Is this a toughie , yes sure. Probably one of the differentiating Qs
Is it wrongly set , no I think, it is brilliantly set.

Sorry, I beg to differ. The solution is actually from my 2 dc. She has advance training in Physics and knows newtonian mechanics and vectorisation. She pointed out to me the question context is only on whether the object is stationary or not. I agree with her that the question depends on the presence and direction of the force which was not clearly specified and that all the question says is that the object is stationary.
I think there should be other kids who are advance in science training who may have been penalised by such a question and perhaps think out of the box. (being kiasuparents)

[Laura02]

I agree with AWSP. If any assumptions are made, they should be stated in their question. If we are really trying to teach our children the correct "scientific method", then all the conditions under which a scientific experiment is carried out should be stated, and not assumed.

[Sun_2010]

AWSP:

Sun_2010:

[quote=\"AWSP\"]The precise answer is :

a) whether there is any friction or not depends on whether there is any force applied on the object or not and the direction that it is applied. If on the slope, a force is applied such that there is a component of the same magnitude that is opposite and equal to the vector force due to gravitational force, the frictional force will be zero as well.
b) likewise if there is any force applied such that a net horizontal resultant vector force exist on the object on the horizontal surface, there is friction (whether it moves or not).
I dont think all these are spelt out clearly in the question. The setter did not specify the forces applied and he could also not specify because even if he did, in order to comprehend the full implication, the student need to know how to vectorise the forces and newton's 1st and 3rd law.
This is an extreme case of a setter who is trying to test for \"intuition\" but does not have sufficient knowledge to set the context properly.
In my opinion, it is an \"illegal\" question and we should challenge it with MOE.

Beg to differ. If there is no mention of any external force in the question or the diagram, it just means there is no such external force acting on the object. The only force that is assumed in such cases is that due to gravity.

While P6 students donot need to know about components of force.and stuff, it should be common sense that to move an object down a slope is easier than that required to move it on a horizontal surface. And that is because of gravity aiding it. And that gravity does not help in moving an object horizontally. What I mean by that- if I want to push an object horizontally then I could push (exert a force) horizontally, or even at an acute angle. But if I were to push it down no matter how hard, still it would not move at all.

Friction is said to be the force that opposes motion. This is taught in the syllabus.

IMHO, children a keen interest for physical sciences are likely to conclude this. There are children who think about why when they play be it down the slide ( the higher the inclination, faster they slide, the longer the slide the greater the speed they hit the ground ) , with tops, ball games, carroms , science is aplenty. Being able to associate that with what you have read is what makes scientific thinking.
Again, IMO,
Is this a toughie , yes sure. Probably one of the differentiating Qs
Is it wrongly set , no I think, it is brilliantly set.

Sorry, I beg to differ. The solution is actually from my 2 dc. She has advance training in Physics and knows newtonian mechanics and vectorisation. She pointed out to me the question context is only on whether the object is stationary or not. I agree with her that the question depends on the presence and direction of the force which was not clearly specified and that all the question says is that the object is stationary.
I think there should be other kids who are advance in science training who may have been penalised by such a question and perhaps think out of the box. (being kiasuparents) :)[/quote]Nice having this conversation, makes me think.
Just my opinion,
In a way I agree , primary school science needs to be taken with a big pinch of common sense. Actual calculations using complex scientific formula and pure scientific jargon etc is not needed. But an understanding of the basic principle is a must. So some basic assumptions is perfectly ok.

For instance , handles for pans are made of Bakelite , wood etc - the traditional insulators. My daughter when she was in p3 was shocked and could not believe that some pans in my kitchen have metal handles that do not become hot. Technology has advanced a lot, even rubber can be made with great variations in its properties. But we explain from the basic properties of the materials. I remember science work time with DD was filled with so much arguments, how that is not the way psle science answers , how her teacher knows and I don't - that things are different now, sometimes even telling that her teacher doesn't know ... :roll:

It's good to know more , but try not reading too much into simple applications. Some GEPpers I know face this problem. When the grasp of advanced knowledge strong, it should come with the skill to scale back, to understand when assumptions are ok. It comes back to the point of understanding what is it the question is trying to test.

[Sun_2010]

Laura02:

I agree with AWSP. If any assumptions are made, they should be stated in their question. If we are really trying to teach our children the correct \"scientific method\", then all the conditions under which a scientific experiment is carried out should be stated, and not assumed.

If a diagram shows an object is at rest and no indication of force acting on it, that means no external forces are acting on it.

And unless it is stated to be on any other planet or space, we can safely assume that gravity is acting on it and it is acting downwards.

I dunno if it is just me, but to be these assumptions are pretty basic. Maybe be I :siao:

[Sun_2010]

sleepyqueen:

Oh mine the answer seems long. My DS would just give a short and sweet answer to it as usual. hmm..like that how to score?!?

I think this was an McQ

Anyway that was a very detailed explanation. Short answers explaining the precise points are always better . So your DS is doing the right thing

[AWSP]

@sun2010

Precisely the concept is accurate and is not wrong and all factors are considered including the grey areas. Do I fault a child for not having the "skill" to scale back. Do we accept that an answer that is thorough and indicate strong concept and which if answered at O levels, A levels and above is a superior solution BUT yet marked wrong at PSLE for a) "reading too much into simple applications"
b) "not trying to apply common sense" and b) " that is not the way PSLE should be answered"? Ultimately, has our PSLE science gone too far into intuition testing without proper concept grounding that in reality we are testing for guessing? - my 2 cents worth.

[AWSP]

Sun_2010:

Laura02:

I agree with AWSP. If any assumptions are made, they should be stated in their question. If we are really trying to teach our children the correct \"scientific method\", then all the conditions under which a scientific experiment is carried out should be stated, and not assumed.

If a diagram shows an object is at rest and no indication of force acting on it, that means no external forces are acting on it.

And unless it is stated to be on any other planet or space, we can safely assume that gravity is acting on it and it is acting downwards.

I dunno if it is just me, but to be these assumptions are pretty basic. Maybe be I :siao:

I would concur that there is no line drawn showing the forces. Anyway any attempt in doing so would be quite beyond the ordinary syllabus of P6. But the question is trying to equate stationarity with absence of forces. This is not true. A student who has knowledge into newtonian mechanics would look for balance of forces ie if there is a net force and come to conclusion that it is not spelt out (and ordinarily, this would be done so very specifically at any exams at a higher level). It could therefore be concluded that in the event of an application of any force applied in an appropriate direction even if the object is not moving, there is friction. (Anyway, this is again outside the P6 syllabus). Note: the number of time I am saying \"out of the syllabus\" My main contention has always been it is extreme testing under the guise of \"application testing\": an unnecessary evil of PSLE.

[AWSP]

Sun_2010:

Laura02:

I agree with AWSP. If any assumptions are made, they should be stated in their question. If we are really trying to teach our children the correct \"scientific method\", then all the conditions under which a scientific experiment is carried out should be stated, and not assumed.

If a diagram shows an object is at rest and no indication of force acting on it, that means no external forces are acting on it.

And unless it is stated to be on any other planet or space, we can safely assume that gravity is acting on it and it is acting downwards.

I dunno if it is just me, but to be these assumptions are pretty basic. Maybe be I :siao:

I would concur that there is no line drawn showing the forces. Anyway any attempt in doing so would be quite beyond the ordinary syllabus of P6. But the question is trying to equate stationarity with absence of forces. This is not true. A student who has knowledge into newtonian mechanics would look for balance of forces ie if there is a net force and come to conclusion that it is not spelt out (and ordinarily, this would be done so very specifically at any exams at a higher level). It could therefore be concluded that in the event of an application of any force applied in an appropriate direction even if the object is not moving, there is friction. (Anyway, this is again outside the P6 syllabus). Note: the number of time I am saying \"out of the syllabus\" My main contention has always been it is extreme testing under the guise of \"application testing\": an unnecessary evil of PSLE.