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Sunday, October 3, 2010

Mengenali Variables -pembolehubah

Jawapan bagi soalan Inference

Plant B is higher / bigger  than A because its get enough fertiliser / water / nutriens / sunlight.
pokok B lebih tinggi / besar daripada A kerana mendapat baja / air / nutrients/ cahaya matahari yang mencukupi.


VARIABLES


Bagaimana untuk kita mengenal ketiga2 pembolehubah ini ? Biasanya pelajar kita tidak dapat membezakan ketiga-tiga pembolehubah ini. Justeru itu mereka tidak dapat menguasai bahagian B.

The Variables

1. Manipulated variable or What to change. (wto)
2. Responding variable or What to observe/measure (wtc) (every year)
3. Constant variable or What to keep the same (wts) (2003,2004,2006,2007,2008)

1. What to observe/measure (wto)
   
-          Thing that is being observed / measured /investigated / recorded / the result of an
      investigation.

2. What to change (wtc)
     
-          Thing that is changed or being manipulated in an investigation and it has an effect on
      thing that is observed.

3.  What to keep the same (wts)
    
-          Thing that is always the same and kept constant  in an  investigation. 


Examples of questions:

a)                  Based on the investigation, state:

            i)  what to change / thing to change :   ____________________________
           ii) what to observe / thing to observe/measure : _____________________

b)         State what to change in the investigation above
           ___________________________________________________________

c)        Write down two variables from the investigation above:
  
           i)   _________________________________________________________         
          ii)   _________________________________________________________

d)        From the data given, identify what to:
  
           i)   keep the same :   ___________________________________________
          ii)   to change   :  ______________________________________________
         iii)   to observe/measure : ________________________________________

e)       State what is kept the same in the investigation.
          ____________________________________________________________


EXERCISES


1.                  Razak, Kamila and Suresh conduct a study to determine the relationship between the distance of the light source from the object and the length and the size of the shadow. They record their observations in the following table.
Razak,Kamila dan Suresh mengendalikan satu kajian untuk menentukan hubungan antara jarak sumber cahaya dari objek dengan panjang dan saiz bayang-bayang.Mereka telah merekodkan pemerhatian dalam jadual di bawah.


Distance of light source from object (cm)
Jarak sumber cahaya dari objek
Length of shadow (cm)
Panjang bayang-bayang
Size of shadow (cm)
Saiz bayang-bayang
6
20
16
10
16
X
14
12
8
18
8
6


a.                   Based on the result above, state:


i.  What to change (manipulated variable)

    ……………………………………………………………………………………

ii. What to observe (responding variable)

    ………………………………………………………………………………

2.                  Three containers R,S and T, containing equal amounts of garden soil are planted with bean seedlings of the same height. The seedlings are planted 5 cm from each other. The container are left in the open and watered with the same amount of water daily. After three weeks the average height of the seedlings in the containers are taken. The results are shown in the table.


Container
Number of seedlings
Average height of seedlings
P
3
16 cm
Q
6
12 cm
R
9
8 cm

           In the investigation, state

            i.   what is being changed

               ……………………………………………………………………………………………

            ii.   what is being measured
               ……………………………………………………………………………………………
           iii.   what is kept the same

                   …………………………………………………………………………………………

3.                  Four white mice are put into cage M and 12 into cage N. The cages are of similar size. In each cage, the number of males and females are the same . The mice in cage N are given the same amount of food and water as the mice in cage M each day. Each of the mice in the cage M and N is weighed after 3 weeks. The average weight of the mice in each cage is obtained.


Cage
Number of mice
Average mass of the mice
M
4
72 g
N
12
50 g



a.                   In the investigation above, state

i.                    What is being changed

……………………………………………………………………………

ii.                  what is being measured

……………………………………………………………………………

iii.                what is kept the same

………………………………………………………………………

4.                  In an investigation, three axes with different widths are used to chop wood. The table below shows the results of the investigation.


Axe
P
Q
R
Width of the back of the blade (mm)
3
6
9
Number of wooden block chopped in 30 minutes
4
8
12


a.                   What is kept the same in this investigation?

………………………………………………………………………………


b.                  State two variables from the investigation above.

i)  ……………………………………………………………………………….

ii)……………………………………………………………………………




5.                  100ml of water is poured in a boiling tube and the temperature of water is measured. Then, the water is heated every 2 minutes until the minute of 6


Time (minute)
0
3
6
Water temperature (˚C)
28
40
52


               State the thing that is kept the same in the investigation.

              …………………………………………………………………………………….            


6.                   An investigation is carried out to study the relationship between consumers and their sources of food in a habitat. It involved rats and snakes in a paddy field. The observations in the investigation are recorded in the following table.


Week
1
2
3
4
Number of snake
9
14
18
23
Number of rats
48
38
32
22


a.                   In the investigation, state

i.                    What is being changed

……………………………………………………………………………

ii.                  what is being measured

……………………………………………………………………………

iii.                what is kept the same

………………………………………………………………………


.         7.       The table below shows a result of the investigation that is carried out by   
                    Mariah.


Number of straws
Weight that can be supported ( kg )
3
0.4
6
1.0
9
1.4
12
2.0


a)      State
            i)        What to change : _____________________________________

           ii)        What to observe: _____________________________________
      8.   The table below shows the time taken by four pupils to complete their Mathematics test.

Pupil
Time taken to complete the test ( minute )
Rafiq
5
Akmal
10
Danish
20
Azhar
12

           
a)      In this activity,

i)                    What is kept the same : ______________________________________________

ii)                  What is measured       : ______________________________________________

iii)                What is being changed : _____________________________________________

9.        The table shows an observation of an experiment that is conducted by a few pupils. Four
       different height of objects were used to support weight.


Object
P
Q
R
S
Mass that can be supported(g )
50
100
150
200

a)      State the 

i)                    Manipulated variable :__________________________________

ii)                  Responding variable   : _________________________________


    

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