Q&A - PSLE Science

[atutor2001]

Zack7:

no. the fact that the independence assumption holds true for most materials shows that it is good.

i go back to F=ma

imagine you push a jelly

we know that in real life, it will not conform to F=ma. you have to take into account the viscosity , tensile strength, stress deformity etc...

so are you going to say F is dependent on variables more than m and a and etc...?

no. you say F is ma with a host of assumptions. like constant mass. etc... and other variables like those named above not playing significant roles.

and of course, just like in friction, F=ma is not a good gauge for jelly as opposed to a hard object.

and not everything that science describes is intuitive. it doesn't mean in your daily life contact friction appearing to depend on surface area is a justification that it has dependence.

I think F=ma may be quite at good gauge for the acceleration of a jelly if the acceleration is not too big to cause distortion to the surface of the jelly.

When instability of the surface occurs, scientists are aware of its effect and formulas have long been developed to take care of that, way back to 1950.

Therefore, F=ma is applicable only if there is no distortion to the surface of the object. In sec sch, they will limit their knowledge to F=ma for solid. But in university, I am sure they will be made aware that F=ma is totally not applicable for liquid or gas. There are many established equations for them to understand and apply.

Back to frictional force where F=uN, although the change in the coefficient \"u\" with respect to the contact area is negligible for most materials, we cannot ignore that \"u\" is actually dependent on the contact areas because many of these materials where the \"u\" changed drastically with the area are common materials that the kids are exposed to in their daily life.

[Michaelia0816]

Pls help me! It was about living together.

What is the two factors that may affect the size of the pond community?
You may list more than 2 for me to choose!!!

[G Tan]

Michaelia0816:

Pls help me! It was about living together.

What is the two factors that may affect the size of the pond community?
You may list more than 2 for me to choose!!!

A lot of answers lah, it is the question in process skills worksheet

1) availability of food
2) onset of diseases
3) .........

[Zack7]

Michaelia0816:

Pls help me! It was about living together.

What is the two factors that may affect the size of the pond community?
You may list more than 2 for me to choose!!!

biotic (living) and abiotic (non-living) factors

[Michaelia0816]

Oh thank you both! I will keep it in mind!

[atutor2001]

Michaelia0816:

Pls help me! It was about living together.

What is the two factors that may affect the size of the pond community?
You may list more than 2 for me to choose!!!

Hi Michaelia0816

I don't think the question you have posted is the original one. In science, the question is extremely important and we need to understand the question first before attempting to answer it.

If the question is really \"What are the two factors that may affect the size of the pond community?\", then there is no answer because the words \"the two\" means those two factors they are asking for has been made known to us and cannot be changed. That is, we cannot put in any other 2 factors. However, there is nothing in the question that indicates which 2 factors they are asking for (unless there are other info given in the question). Putting \"biotic\" and \"abiotic\" as the answer will also be wrong because those are \"types of factors\" and not actual factors. (as an example : Name 2 plants found in the community. The answer cannot be \"flowering\" and \"non-flowering\" plants as those are \"types of plants\". The question is asking for 2 plant names.) Therefore, understanding of the question is important.

[Zack7]

atutor2001:

Michaelia0816:

Pls help me! It was about living together.

What is the two factors that may affect the size of the pond community?
You may list more than 2 for me to choose!!!

Hi Michaelia0816

I don't think the question you have posted is the original one. In science, the question is extremely important and we need to understand the question first before attempting to answer it.

If the question is really \"What are the two factors that may affect the size of the pond community?\", then there is no answer because the words \"the two\" means those two factors they are asking for has been made known to us and cannot be changed. That is, we cannot put in any other 2 factors. However, there is nothing in the question that indicates which 2 factors they are asking for (unless there are other info given in the question). Putting \"biotic\" and \"abiotic\" as the answer will also be wrong because those are \"types of factors\" and not actual factors. (as an example : Name 2 plants found in the community. The answer cannot be \"flowering\" and \"non-flowering\" plants as those are \"types of plants\". The question is asking for 2 plant names.) Therefore, understanding of the question is important.

Hah still so full of yourself?

Asker requested for more than two factors. I gave him the broad groups to choose from

[atutor2001]

Zack7:

Hah still so full of yourself?

Asker requested for more than two factors. I gave him the broad groups to choose from

Your reply was \"biotic (living) and abiotic (non-living) factors\" Please be kind to the other readers by elaborating that \"you can chose from these 2 broad groups, or adding the word \"type\" before factor. There are many students reading this forum. They might misunderstood those two as factors and used them.

[isetan]

I dd got a question from her teacher for weekend hw.


If a rocket runs out of fuel in the space, will the rocket stops moving or still moves towards the direction of nearest planet due to magnetic attraction?

Can anyone ans? Thanks.

[Zack7]

atutor2001:

Zack7:

Hah still so full of yourself?

Asker requested for more than two factors. I gave him the broad groups to choose from

Your reply was \"biotic (living) and abiotic (non-living) factors\" Please be kind to the other readers by elaborating that \"you can chose from these 2 broad groups, or adding the word \"type\" before factor. There are many students reading this forum. They might misunderstood those two as factors and used them.

Well, anyone with 'common sense' as you so crudely like to use, should know how to differentiate. And not blindly absorbing all the comments here.