## Sunday, February 28, 2010

### [Science Form 2] Experiments On Air Pressure At Home

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Experiment!

Have you ever tried carrying out experiments on air pressure at home? Let's see how we can inflate a balloon inside a bottle.

Inflate a balloon inside a bottle? Is that possible?

All you need is a bottle, a bowl, some hot water, some ice-cold water and a balloon.

Now, let's start the experiment.
1. Fill the bottle with hot water.
2. Fill the bowl with the ice-cold water.
3. Let both sit for one minute.
4. Empty out the bottle.
5. Stretch the balloon over the mouth of the bottle.
6. Set the bottle in the bowl of cold water.

This is what you would observe... an inverted inflated balloon in the bottle!

How do we explain this phenomena?

First of all, air contracts and takes up less room when cooled. Similarly, it expands when it gets hot. The hot water heats the bottle. When the bottle is poured out, the heated bottle then heats the air in it. When the bottle is placed in the bowl of cold water, the air inside the bottle cools and contracts, causing the air pressure inside the bottle to decrease. When this happens, the higher air pressure outside the bottle causes the air outside to be drawn in, pulling the balloon in and inflating it inside the bottle.

## Thursday, February 18, 2010

### [Science Form 3] Transmission & Distribution

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• The electricity distribution system includes:

• National Grid Network, which carries electricity to the main substation
• Consists of a network of cables that carries electricity with a voltage of 66kV, 132kV or 275kV
• It connects all the power stations in our country.

• Transformer station

• Switch zone, which is located in various places
• It is equipped with circuit breakers to automatically cut off the circuit if a short circuit occurs.

• Main substation, where voltage is lowered by a step-down transformer to 33kV
• This high voltage is supplied to heavy industries like vehicle manufacturing factories.

• Substation branches, where voltage is lowered by a step-down transformer to 11kV
• This is supplied to light industries like electronic factories.

• The voltage to housing estates is 240V.

### [Science Form 3] The Alternatives

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• Electric generators like thermal, diesel, nuclear and gas turbine generators use raw materials that are non-renewable sources of energy.

• Solar energy is:
• obtained from the sun
• an electrical energy
• used to supply electrical energy to:
• Satellites
• Electronic calculators
• Clocks
• Certain vehicles

• Biomass
• Organic material that can be charged into energy
• Energy can be released from biomass through
• Burning
• Fermentation
• Chemical reaction or bacterial action

• In a fermentation process, the mixture of yeast and sugar is changed into carbon dioxide and ethanol fuel.
• Biomass is in large supply and is a renewable source of energy that can be used as a substitute for fossil fuel.

## Thursday, February 11, 2010

### [Biology Form 4] The Haploid Cells

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Another type of cell division is known as meiosis. Meiosis involves the division of a cell into four daughter cells. It takes place only in reproductive organs (eg: in the testes and ovaries of animals and in the anthers and ovules of plants).

The purpose of meiosis is to produce gametes or reproductive cells so that sexual reproduction in organisms can occur.

Unlike those produced through mitosis, these daughter cells are usually not genetically identical to their parent cells. The chromosomes in each daughter cell are half the number found in the parent cell.

While cell division occurs once during mitosis, cell division occurs twice during meiosis. Meiosis I is followed by Meiosis II.

In Meiosis I, the cell divides into two daughter cells, whose number of chromosomes is halved. In Meiosis II, each of the two daughter cells divides into another two daughter cells, resulting in four haploid daughter cells (with the same halved number of the original chromosomes).

Shown in the following diagram are the basic differences between mitosis and meiosis.

## Monday, February 08, 2010

### [Science Form 3] Reactions

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Most metals react with oxygen to form metal oxide.

Metal + Oxygen -------> Metal oxide
Eg:
• Zinc + Oxygen -------> Zinc oxide
• Aluminium + Oxygen -------> Aluminium oxide

Most metals react with sulphur to form metal sulphide

Metal + Sulphur -------> Metal sulphide
Eg:
• Zinc + Sulphur -------> Zinc sulphide
• Iron + Sulphur -------> Iron sulphide

Metal + sulphide -------> Final product
1. Magnesium + Sulphur ----heat---> Magnesium sulphide
2. Aluminium + Sulphur ----heat---> Aluminium sulphide
3. Zinc + Sulphur ----heat---> Zinc sulphide
4. Iron + Sulphur ----heat---> Iron sulphide

Metal + oxide -------> Final product
1. Magnesium + Oxygen ----heat---> Magnesium oxide
2. Aluminium + Oxygen ----heat---> Aluminium oxide
3. Zinc + Oxygen ----heat---> Zinc oxide
4. Iron + Oxygen ----heat---> Iron oxide

## Sunday, February 07, 2010

### [Physics Form 5] Rendezvous Point

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Situation:
Two waves, Wave 1 and Wave 2, of the same frequency, wave length and amplitude, approach each other.
1. State the principle applied in the phenomenon above.
Principle of superposition.

2. Define the principle.
When two coherent waves travelling in opposite directions meet, the resultant displacement is the vector sum of the displacements of the two waves at the point of interference.

3. What is happening at Y and what is X?
At Y, where two pulses of the waves overlap, constructive interference occurs. X is the resultant pulse of the overlap.

4. What is happening at U and what is V?
At U, where a pulse of a crest and a pulse of a trough overlap, destructive interference occurs. V is the resultant pulse of the overlap. It shows zero displacement; a state of calmness or no wave pulse.

5. What is expected after the meeting of Wave 1 and Wave 2?
The two waves travel in opposite directions along their original paths, unaffected by each other.
Note: Interference only occurs at the meeting point between two pulses of waves.

### [Physics Form 4] In Locomotion

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Acceleration, velocity and displacement are the physical quantities often used to describe the motion of objects. These quantities are also known as the quantities of kinematics.

What are acceleration? Acceleration is a derived vector quantity that describes the motion of any object in terms of change in velocity per unit time. To be specific, it describes the increase in velocity of an object in one second.

Ex: The car is moving with a constant acceleration of 4ms-2. This means that the velocity of the car increases 4ms-1 every 1s. This occurs constantly throughout the motion of the car.

What is meant by velocity? Velocity is a derived vector quantity that describes the motion of any object in terms of change in displacement per unit time.

Constant velocity means the velocity is fixed throughout the motion. It also means the displacement covered by object is constant every one second.

The trolley above is moving down an inclined plane at the constant velocity of 1ms-1. This means that as the trolley is moving down the inclined plane, it covers a displacement of 1m every 1s. If the inclined plane is 3m long, it will take the trolley 3s to reach the bottom.

What is displacement? Displacement is a straight line distance measured from the initial point (reference point) to the final point.

Constant displacement is another way of saying that the object is stationary. When a displacement is constant, it means the final position is not changed. Hence, the object is resting at the final position.

Zero displacement is achieved when the final position meets the initial position. Hence, there is no distance between the final and initial positions.

## Thursday, February 04, 2010

### English boost for 7 schools

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NST
2010/02/04
By Nusaybah Mohd Asri

KUALA LUMPUR: The Federal Territory Zakat (tithe) Collection Centre-FT Islamic Council (PPZ-MAIWP) has agreed to sponsor RM20,000 worth of Berita Harian and New Straits Times newspapers and Malaysia 50 Years history books to selected schools.

Seven schools that have started receiving copies of the newspapers are Sekolah Menengah Kebangsaan (SMK) Perempuan (P) Jalan Ipoh, SMK Puteri Titiwangsa, SMK Sinar Bintang, SMK Raja Ali, Sekolah Kebangsaan (SK) Cheras, SK Bandar Tun Razak (2) and SK Seri Anggerik.

These schools have been getting 50 copies of Berita Harian and another 50 copies of the New Straits Times every week on Monday, Tuesday and Wednesday starting Feb 2.

The 10 schools that received the Malaysia 50 Years history books are SMK (P) Bandaraya, SMK Taman Setiawangsa, SMK Bandar Tun Razak, SMK Taman Maluri, SM Alam Shah Putrajaya, SK Taman Setiawangsa, SK (1) Batu 4 Jalan Ipoh, SK Wangsa Jaya, SK Setapak Indah and SK Jalan Peel.

The books were published by the publication unit of the Information, Communications and Culture Ministry and the Star Publication.

PPZ-MAIWP chairman Datuk Mustafa Abdul Rahman said the sponsorship programme was a token of appreciation for these schools that had succeeded in increasing the amount of tithes through salary deductions of their staff, including teachers and headmasters.

Mustafa also said PPZ-MAIWP would provide financial assistance to the schools to organise "programmes of excellence" and students' personality development activities.

"We will consider giving financial assistance if, needed, as the programmes can help enhance students' achievements in the primary and secondary schools.

"I hope our sponsorship programme can instil awareness among students on the importance of paying tithes as well as being focused in their studies." he said.

Also present was Bangsar-Pudu Education Department deputy director Jamaluddin Abdullah.

## Tuesday, February 02, 2010

### [Mathematic Form 4] Lower or Upper?

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When quantities are measured, their data can be grouped into several classes. The range of each class is called the class interval.

For a class interval of 70 - 79, the lower limit is 70 and the upper limit is 79.

For a class interval of 80 - 89, the lower limit is 80 and the upper limit is 89.

The lower boundary of each class refers to the middle value between the lower limit of the class and the upper limit of the previous class.

The upper boundary of each class refers to the middle value between the upper limit of the class and the lower limit of the following class.

The size of a class interval is the difference between the upper boundary and the lower boundary of the class.