Q&A - PSLE Science

[tianzhu]

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

I was looking at an old edition of PSLE Science Guide from MC.

Perhaps you may want to refer to the chapters on Living together and The Environment. It might help to give you some pointers. Please check your new edition of science guide as the chapters might be different.

First, as defined in the book, a pond community is made up of populations of organisms that live in the water as well as on land near the pond.

To enable the organisms to live and grow in the habitat, they must have necessary conditions for growth and reproduction.

If you are talking about some limiting factors in the pond community,you may touch on factors like

1)Temperature
2)Light
3)Carbon dioxide
4)Oxygen
5)Water
6)Pollution
7)Disease causing
8)Predator-Prey relationship

I’ll leave it to you to do some reading from your books.

Best wishes

[Winx5015]

Topic on Interactions - Types of Forces


(1). Explain why the steel rod moved faster on the plastic washing board than it did on the thin wooden ramp?

Thanks.

[tianzhu]

Winx5015:

Topic on Interactions - Types of Forces


(1). Explain why the steel rod moved faster on the plastic washing board than it did on the thin wooden ramp?

Thanks.

Hi

If I remember correctly, friction is one of the types of forces covered under “Interactions” in PSLE science.

I guess your question is one part of an open ended question involving experiment on inclined planes of different materials.

In PSLE Science, students learned that friction acts to reduce the speed of a moving object. Depending on the layout of the experiment in your question, you may apply this concept to explain why the steel rod moved faster on the plastic washing board than it did on the thin wooden ramp. There is less friction on the plastic washing board than the wooden ramp.

Best wishes

[Winx5015]

thanks tianzhu:)

[atutor2001]

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.

Hi isetan

This is a tough \"application\" question for primary student.

Lets first list down the possible effects of a force on an object :

1. A force can cause a moving object to move faster or slow down.
2. A force can cause a moving object to come to a stop.
3. A force can cause a moving object to change its direction.

Lets now look at the possible effect of the force from the fuel on the rocket. The effect of this force could be :

1. to move the rocket faster (it is unlikely to slow down or stop the rocket)
2. to change/control the direction of the rocket (a force is needed to control the direction we want to rocket to head to)

Therefore, when this force from the fuel is removed, the rocket will not stop but continue to move at a constant speed (cannot go faster as there is no force to push it to move faster), in the same direction as when the rocket is heading at the time when the fuel is cut off (as there is no force to change its direction).

If at that time the rocket is near earth or another planet and is attracted by the gravitational force of earth or that planet, this attractive force will then pull the rocket to the centre of earth or that planet.

If there is no planet nearby, the rocket will continue to move straight ahead at a constant speed until it enters the gravitational field of a planet and will then be pulled to the centre of that planet.

I don't think the force of attraction by a planet is magnetic force (as stated by the teacher). If I remember correctly, it should be gravitational force.

Hope it is of help.

[Michaelia0816]

Thanks both for your efforts!!! I would take note of that, after teacher marks it, I would know the " exact" maybe lah answer. I would post it too.

[Michaelia0816]

Tianzhu, I now going to check for it. I would post correct answer for us to take note in cause of psle, dude!!!

[Michaelia0816]

Ok I could maybe find that conditions in their surroundings, the presence of food source, the supply of oxygen, competitor, temperature and amount of water.

[Michaelia0816]

And also all of your factor that you listed out. Sorry that I forgot to edit it in even I knew how to!!!

[Michaelia0816]

This following characteristic of Animal G are describe in the following tables:

Animal G:
- Small wings
- Webbed feet
- Cannot fly
- Streamlined body
- Bones heavy and solid
What kind of animal are Animal G? Why it can’ t fly?
( Another kind of answer is accepted)