Q&A - PSLE Science

[php]

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.

http://answers.yahoo.com/question/index?qid=20070614070227AAP9Nge

[Michaelia0816]

Question help!

In what ways does fish depend on plants and plants depend on fish for survival?
My answer is likely fish need oxygen produced by plants and plants needs carbon dioxide by fish.
But my tutor said it can still add on some, she will not help me ,can you help!

[php]

Michaelia0816:

Question help!

In what ways does fish depend on plants and plants depend on fish for survival?
My answer is likely fish need oxygen produced by plants and plants needs carbon dioxide by fish.
But my tutor said it can still add on some, she will not help me ,can you help!

http://answers.yahoo.com/question/index?qid=20101225084628AAxHFZn

[Michaelia0816]

Thank php for helping to find such list!!!

[isetan]

Thanks Php, well explained!

[atutor2001]

php:

atutor2001:

[quote=\"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.

.....

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.

http://answers.yahoo.com/question/index?qid=20070614070227AAP9Nge[/quote]Thank you php for the link. I have totally forgotten about the orbit part. My apology to isetan for the error.

[Michaelia0816]

Then what happened to it when it crash on island not earth? No fuel?

[tianzhu]

Michaelia0816:

Question help!

In what ways does fish depend on plants and plants depend on fish for survival?
My answer is likely fish need oxygen produced by plants and plants needs carbon dioxide by fish.
But my tutor said it can still add on some, she will not help me ,can you help!

Hi

Great, you’re a lucky girl as not all students have access to tuition.

I recall having seen a popular question on interdependence of plants and animals in a terrarium.

Some pointers from the Science guide and textbooks.

Green plants provide oxygen for the animals when they photosynthesise. Animals breathe out carbon dioxide that the plants need for photosynthesis. Some animals find shelter or feed on plants. At the same time, the animals’ wastes act as fertilisers to help the plants grow.

Best wishes

[Michaelia0816]

actually my mum is my tutor, thank to her, i got to Singapore Primany Science Olympaid. Never got on too hard

[Michaelia0816]

I just need more clearer detail to help me, so i might be posting more about similar question like this