Thursday, October 28, 2010

Tip- SPM Fizik kertas 3

A student investigate how the extension of a spring changes with the load acting on a spring.
Diagram 1.1 and 1.2 show what happens when two different loads are hang on two identical springs.


Based on the information and the observation above:
Berdasarkan maklumat dan pemerhatian di atas:

a) State one suitable inference that can be made
Nyatakan satu inferens yang sesuai [1 mark]



* pesanan :
baca soalan dengan teliti dan carikan pembolehubah yang tersurat dalam maklumat yang diberi.
Contohnya pemboleh ubah boleh laras ( manipulated variable ) ialah beban load // force // mass) yang digunakan , dan pemboleh ubah bersandar ( responding variable) ialah pemanjangan spring. ( extention of spring ).


Sambungkan pemboleh ubah yang dikesan dengan kata kunci seperti
i) MV influences RV
ii) RV is influenced by MV
iii) RV depends on MV.


b) State one appropriate hypothesis for an investigation
Nyatakan satu hipotesis yang sesuai dikaji [1 mark]


* pesanan :
Tuliskan hubungan MV dengan RV .



c) With the use of apparatus such as a spring, slotted weights and other apparatus, describe an experimental framework to test your hypothesis stated in 2(b)
In your description, state clearly the following:


Menggunakan alat radas seperti spring, jisim berslot dan lain-lain radas yang sesuai, terangkan suatu rangka kerja eksperimen untuk menguji hipotesis anda di 3(b).
Dalam penerangan anda, jelaskan perkara-perkara berikut



(i) The aim of the experiment
Tujuan eksperimen


* pesanan :
Gunakan kata kunci
i) to study...
ii) to investigate...



(ii) The variables in the experiment
Pembolehubah didalam eksperimen


* pesanan :
senaraikan ketiga-tiga pemboleh ubah.


(iii) The list of apparatus and materials
Senarai radas dan bahan

* pesanan :
Alatan yang dicadangkan perlu disaling semula, dan pastikan alatan yang disenaraikan boleh digunakan untuk menguju MV dan RV yang anda cadangkan.
Contoh:
Pembaris (Meter rule ) --> mengukur panjang spring.

(iv) The arrangement of the apparatus
Susunan radas

* pesanan :
Lukiskan dan labelkan susunan radas yang berfungsi.

(v) The procedure of the experiment which include the method of controlling the manipulated variable and the method of measuring the responding variable.
Prosedur eksperimen termasuk kaedah mengawal pembolehubah dimanipulasi dan kaedah mengukur pembolehubah bergerakbalas

* pesanan :
Senaraikan arahan menguju MV dan RV, dicadangkan arahan mengulangi ujikaji sebanyak 4 kali .

(vi) The way you would tabulate the data
Cara untuk menjadualkan data

* pesanan :
Lakarkan jadual berlabel dan tandakan unit kuantiti fizikal.

(vii) The way you would analyse the data
Cara untuk menganalisis data [10 marks]

*pesanan:


Lakarkan graf dengan tandakan MV (di paksi-x) dan RV ( dipaksi-y) pastikan unit yang betul diberi.


Suggested answer:

a) Inference :
The pulling force influences the extension of the spring//
The length of spring is influenced by the pulling force//
Length of spring depends on the force acting on it.

b) Hypothesis:
The bigger the force , the longer the spring.//
When the force(mass) increases, the length of the spring increase

C)
i) Aim:
To investigate the relationship between force //mass and the extension of the spring

ii)
Manipulated variable : Force, F// mass
Responding variable: Extension of spring, x
Fixed variable: Diameter// stiffness of spring/ the initial length, lo/ spring constant of spring,k

iii) List of apparatus/ materials :
Spring, pin, slotted weight, retort stand with clamp, meter rule and plasticine.


iv) Arrangement of the apparatus( with labels )

v)
~ Method of controlling the manipulated variable :
1. Determine the initial length, lo, without any slotted weight hung to the spring.
2. Hang a slotted weight of mass 50 g, (force/weight of 0.5 N) and measure the length of the spring .



~Method of measuring the responding variable :
3. Calculate the extension of the spring, x using the formula ( length l) – (initial length, lo)


~Repeating :
4. Repeat the experiment using mass of 100g, 150g, 200g and 250g (or force, F= 1.0 N, 1,5 N, 2.0 N and 2,5 N)



vi)

Selamat Maju Jaya.











Monday, October 25, 2010

SPM Trial MARA 2010 ~ paper 2 ( Radioactivity )

Question 3


Diagram 3 shows a Geiger-Muller tube (GM tube) and a rate meter which are used to detect the level of milk in containers in a factory.
Table 3 shows the readings recorded by the rate meter for four containers P, Q, R and S when a radioactive source is placed near the containers. The rate meter records a reading of 100 counts per minute when there is no radioactive source nearby.

Rajah 3 menunjukkan sebuah tiub GM dan alat meter kadar digunakan untuk mengesan paras susu di dalam bekas di sebuah kilang.
Jadual 3 menunjukkan bacaan meter kadar bagi empat bekas P, Q, R dan S bila suatu sumber radioaktif diletakkan berhampiran bekas. Meter kadar mencatatkan bacaan 100 bilangan per minit jika tiada sumber radioaktif diletakkan berdekatan.




(a)
Name the radiation emitted by the radioactive source.
Namakan sinar radiasi yang dikeluarkan oleh sumber radioaktif itu.



Hints for solving the problem :
Beta or gamma source are used, depending on the thickness and the density of the material to be measured.


(b)
(i)
Based on Table 3, which container has the least amount of milk?
State one reason for your answer.
Berdasarkan Jadual 3, bekas yang manakah mempunyai kuantiti susu paling kecil?
Beri satu sebab bagi jawapan anda.

Hints for solving the problem :
The reading depends on the milk quantity in the container and it gets higher as the milk is under level.

(ii)
State the actual rate meter reading for Q.
Nyatakan kadar bacaan sebenar bagi Q

Hints for solving the problem :
When there is no radioactive source nearby the detector detect natural background radiation . (cosmic radiation, solar radiation, etc)

(c) The mass of a radioactive source is reduced from 80.0 g to 20.0 g in 30
seconds. Calculate its half-life.

Jisim suatu sumber radioaktif menyusut dari 80.0 g kepada 20.0 g dalam masa 30 saat.
Hitungkan setengah hayat bagi bahan radioaktif tersebut.

Hints for solving the problem :
The half-life of a radioisotope is the average time it takes for half of the remaining radiative atoms to decay to a different atom.

Suggested answers:
a) beta because it can penetrate box and liquid and is less
dangerous than gamma.
b)
(i) R has the least a mount of milk. highest mean it allow more beta to passes though.
(ii) 566 - 100 = 466 counts per second
c) 80 --> 40 --> 20
it undergo 2 half-life.
half life = 30/ 2 = 15 secs



Friday, October 22, 2010

Trial Selangor 2010 ~ paper 2 ( transformer )

Question 10 :( Selangor trial 2010)

Diagram 10.3 shows a simple step-up transformer.
Rajah 10.3 menunjukkan sebuah transformer injak naik yang ringkas.

i) Explain why step-up transformers are used in the transmission of electricity.
Terangkan mengapa transformer injak naik digunakan dalam penghantaran elektrik.

Notes :
A transformer changes the magnitude of an alternating current voltage. ( Direct current is not transformed, ad dc does not vary its magnetic fields)
A step-up transformer supplied an output voltage that higher that the input voltage.

* Penting transformer hanya meningkatkan voltan elektrik sahaja. Elakkan tulis arus elektrik ( Current).

(ii) You are required to modify the transformer in Diagram 10.3 so that it can be used as a laptop adapter with high efficiency and output of 20 V direct current.
Your suggestions and explanation should be based on the following aspects:

Anda dikehendaki mengubahsuai transformer pada Rajah 10.3 supaya ia boleh digunakan sebagai adapter komputer riba yang berkecekapan tinggi dengan mengeluarkan output arus terus 20 V.
Cadangan dan penjelasan anda haruslah berdasarkan aspek-aspek berikut:

a.
Type of the core used.
Jenis teras yang digunakan.

Note:
The alternating current flowing through the transformer continually magnetises and demagnetises the core. work has to be done to change the magnetic field in core which contributes to energy loss.
Use cores made from soft-iron can be easily easily magnetised and demagnagtised.

Materials and diameter of the wire used.
Bahan-bahan dan diameter dawai yang digunakan.

Note:
All wires will have resistance, heat is produced when current flow through them.r
The resistance will reduce as the wire is thicker. ( bigger diameter )

c.
Ratio of the number of tums in the primary coil to the secondary coil.
Nisbah bilangan lilitan gegelung primer kepada gegelung sekunder.

Note:
Ratio of the number of tums in the primary coil to the secondary coil is called turns ratio ( also known as voltage ratio)
* write the primary turns no. first.
Example => 1 to 20 is step-up transformer, whereas a 20 to 1 would be a step-down transformer.

d.
The arrangement of the primary coil and the secondary coil.
Susunan gegelung primer dan gegelung sekunder.

Note:
Electrical energy is lost when a fraction of the magnetic field produced by the primary coil does not link with the secondary coil.

e.
The number of diodes used.
Bilangan diod yang digunakan.

Note:
Two full-wave rectification methods.

Bridge rectifier--> four diode are used
and
center tap rectifier --> two diode are used

suggested answers:

i) The greater the transmission voltage, the smaller the current in the
power lines.
ii) Power loss during transmission due to resistance will be smaller.

a.
-
laminated soft iron core
~ easily magnetised or
demagnetised
~ to reduce the effect of eddy
current .

b.
-copper wire & large diameter
~
reduce heat loss due to
resistance

c.
Np : Ns
240 : 20
24 : 2
12 : 1
~ to reduce output voltage

d.
-Wind the secondary coil on
top of the primary coil
~ to reduce the leakage of
magnetic flux

e.
- 2 or 4 diodes
~to produce full-wave
rectification