Q&A - PSLE Science

[StudentproinMATHandScience]

SAHMwith2boys:

http://i49.tinypic.com/14tx2me.jpg\">


Answer given was (1), can explain why?

I'm a student very good in Science and actually it's quite obvious right?
Conclusions
A:Least dark
B:Less Dark
C:Mediocre dark
D:Very dark
Temperature:
A:lowest
B:2nd lowest
C:2nd highest
D:highest
From here it's quite obvious already.The darker the object is,the higher the temperature it has.Hence answer is (1)
:imcool:

[SAHMwith2boys]

StudentproinMATHandScience:

SAHMwith2boys:

http://i49.tinypic.com/14tx2me.jpg\">


Answer given was (1), can explain why?

I'm a student very good in Science and actually it's quite obvious right?
Conclusions
A:Least dark
B:Less Dark
C:Mediocre dark
D:Very dark
Temperature:
A:lowest
B:2nd lowest
C:2nd highest
D:highest
From here it's quite obvious already.The darker the object is,the higher the temperature it has.Hence answer is (1)
:imcool:

But the temp is A:lowest, B: 2nd highest, 2nd lowest and highest. So is it considered conclusive?

[Verysuperkiasu]

Does anyone know if friction depends on surface area. I mean friction between two concrete surfaces. ( I know air resistance, which is a form of friction, does indeed depend on surface area. )


I ask this question because DD’s teacher said so. But I check guide books - they only say friction depends on the texture of surface - rougher it is, more friction. That makes sense to me. But not sure about surface area though. And how about weight?

[Sun_2010]

Verysuperkiasu:

Does anyone know if friction depends on surface area. I mean friction between two concrete surfaces. ( I know air resistance, which is a form of friction, does indeed depend on surface area. )


I ask this question because DD's teacher said so. But I check guide books - they only say friction depends on the texture of surface - rougher it is, more friction. That makes sense to me. But not sure about surface area though. And how about weight?

If my memory serves me right,
Frictional force does not depend on area of contact.

Frictional force is proportional to Normal force so is proportional to weight of object .

[Garfieldpal]

Sun_2010:

Verysuperkiasu:

Does anyone know if friction depends on surface area. I mean friction between two concrete surfaces. ( I know air resistance, which is a form of friction, does indeed depend on surface area. )


I ask this question because DD's teacher said so. But I check guide books - they only say friction depends on the texture of surface - rougher it is, more friction. That makes sense to me. But not sure about surface area though. And how about weight?

If my memory serves me right,
Frictional force does not depend on area of contact.

Frictional force is proportional to Normal force so is proportional to weight of object .

Sun_2010 is correct. Frictional force does NOT depend on the surface area in contact. Rather, it depends on the weight or mass of the object.

[Alanyklim]

Thx

[clblinym]

http://i49.tinypic.com/14shc9h.jpg\">

This is from RGS 2012 Sa1 Q25
Can anybod here explain why the answer given is 3. TIA. Amy

[clblinym]

http://i49.tinypic.com/2mfnion.png\">

Another one is from Rosyth 2001 SA1 Q8.

The answer given is 2. Can anybody explain why? Many thanks. Amy

[zinc6539]

clblinym:

http://i49.tinypic.com/14shc9h.jpg\">

This is from RGS 2012 Sa1 Q25
Can anybod here explain why the answer given is 3. TIA. Amy

You can observe from the graph that every 50g increase in weight causes the spring to become 10cm longer. The question also states that the relationship is proportionate until 200g. Therefore:

50g - 20cm
100g - 30cm
150g - 40cm

[tomotom0]

Hello can anyone help me with this Q?

The answer given is (3), why isn't it (1)?

The ball bearing should drop very quickly from (1) to (4) due to gravity right?
Like, since at (1), the GPE is at maximum, the GPE would be converted to KE, so it should move the fastest at (1)?

Thanks in advance!

http://i1352.photobucket.com/albums/q659/tomotom0/92d0b24f-973a-44ef-aa33-8ababa9007f1_zps2dd895e3.jpg\">