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SOAL DAN PEMBAHASAN MATERI SUHU DAN PEMUAIAN (SMP KELAS VIII = PAKET 1)

1. Suhu suatu zat menyatakan ...
a. jumlah molekul zat
b. tingkat kenaikan volume zat
c. tingkat panas atau dinginnya suatu zat
d. tingkat pemuaian zat

pembahasan :
suhu atau temperatur adalah besaran yang menyatakan derajat (tingkat) panas atau dinginnya suatu zat

jawaban : c

2. Satuan Internasional (SI) yang digunakan untuk suhu adalah ...
a. celcius                                      b. fahrenheit
c. reamur                                     d. kelvin

pembahasan :
satuan internasional (SI) untuk suhu adalah kelvin karena dalam banyak pengukuran di bidang riset khususnya dalam bidang riset temperatur rendah satuan celcius, reamur, dan fahrenheit menggunakan angka nol dan minus dalam nilai temperatur sehingga menyulitkan perhitungan secara matematis, sehingga ditetapkan bahwa suhu terendah adalah 0 kelvin

jawaban : d

3. Suhu suatu zat diukur dengan ...
a. barometer                               b. termometer
c. higrometer                              d. manometer

pembahasan : 
- barometer adalah alat untuk mengukur tekanan udara luar
- termometer adalah alat untuk mengukur suhu
- higrometer adalah alat untuk mengukur kelembapan udara
- manometer adalah alat untuk mengukur tekanan udara dalam ruang tertutup

jawaban : b

4. Pernyataan berikut ini benar, kecuali ...
a. suhu merupakan besaran turunan
b. alat ukur suhu adalah termometer
c. suhu menyatakan derajat panas sebuah benda
d. molekul-molekul sebuah benda bergetar cepat jika suhu dinaikkan

pembahasan : 
suhu merupakan salah satu besaran pokok

jawaban : a

5. Air tidak dipakai untuk mengisi termometer. Hal ini karena ...
a. volume air tetap
b. tidak memuai ketika dipanaskan
c. memiliki pemuaian yang kecil
d. air membasahi dinding

pembahasan :
alasan mengapa air tidak digunakan untuk mengisi tabung termometer antara lain :
- air membasahi dinding
- tidak berwarna
- jangkauan suhu air terbatas (0 - 100) derajat C
- perubahan volume air sangat kecil ketika suhunya dinaikkan
- merupakan penghantar panas yang sangat jelek

jawaban : d

6. Salah satu keuntungan alkohol sebagai pengisi termometer adalah ...
a. dapat mengukur suhu yang sangat tinggi
b. dapat mengukur suhu yang sangat rendah
c. tidak berwarna
d. tidak membasahi dinding tabung

pembahasan :
keuntungan alkohol sebagai termometer :
- alkohol sangat murah dibanding raksa
- dapat mengukur suhu dengan sangat teliti
- dapat mengukur suhu yang sangat rendah

jawaban : b

7. Keuntungan raksa sebagai pengisi termometer adalah :
(1) tidak membasahi dinding
(2) pemuaiannya tidak teratur
(3) mudah dilihat
(4) titik bekunya rendah
Pernyataan di atas yang benar adalah ...
a. 1, 2, dan 3                                           b. 1 dan 3
c. 2 dan 4                                                d. 4 saja

Pembahasan :
keuntungan raksa sebagai pengisi termometer sebagai berikut :
(1) mudah dilihat
(2) tidak membasahi dinding
(3) jangkauan suhu cukup lebar (-40 sampai 350 derajat C)
(4) merupakan penghantar panas yang baik

jawaban : b

8. Titik tetap atas termometer celcius adalah ...
a. suhu es yang mencair
b. suhu air yang membeku
c. suhu air yang panas
d. suhu air yang mendidih

pembahasan : 
titik tetap atas termometer celcius adalah suhu didih air, sedangkan titik tetap bawah adalah suhu lebur air

jawaban : d

9. Termometer klinis mempunyai daerah ukur antara ...
a. (0 - 50) derajat C                               b. (0 - 100) derajat C
c. (30 - 40) derajat C                             d. (35 - 42) derajat C

pembahasan :
termometer klinis digunakan untuk mengukur suhu tubuh. Karena suhu terendah manusia tidak pernah kurang dari 35 derajat C dan suhu tertinggi tidak pernah lebih dari 42 derajat C, maka angka-angka pada skala didesain antara 35 - 42 derajat C

jawaban : d

10. Pada termometer celcius, titik didih air adalah 100 derajat C. Pada termometer fahrenheit nilai ini sama dengan ...
a. 212 derajat F                                      b. 180 derajat F
c.  132 derajat F                                     d. 32 derajat F

pembahasan :
pada skala fahrenheit, titik didih air adalah 212 derajat C, atau dapat juga dihitung dari rumus konversi skala celcius ke skala fahrenheit sebagai berikut :
dari soal diketahui t derajat C = 100 derajat C, maka :
 

jawaban : a

11. Suhu suatu zat adalah 25 derajat C. Jika diukur oleh termometer skala fahrenheit, maka suhu zat tersebut adalah ...
a. 97 derajat F                                           b. 95 derajat F
c. 77 derajat F                                           d. 45 derajat F

pembahasan :
dari soal diketahui :
t derajat C = 25
maka :

jawaban : c

12. Suhu suatu zat diukur oleh termometer reamur adalah 60 derajat. Bila diukur oleh termometer celcius adalah ...
a. 28 derajat                                               b. 48 derajat
c. 75 derajat                                               d. 80 derajat

pembahasan :
dari soal diketahui t derajat R = 60 derajat
maka :
jawaban : c

13. Titik didih air di permukaan laut adalah ... derajat C.
a. 76                 b. 78                      c. 98                   d. 100

pembahasan :
titik didih air pada tekanan 76 cmHg (tekanan udara di permukaan laut) adalah 100 derajat C

jawaban : d

14. Titik tetap bawah termometer celcius dibuat dengan cara mencelupkan reservoirnya ke dalam ...
a. larutan garam
b. es yang sedang melebur
c. campuran es dan garam
d. air yang sedang mendidih

pembahasan :
pada termometer celcius, titik tetap bawah adalah es yang sedang melebur (titik lebur es) dan titik tetap atas adalah air yang sedang mendidih (titik didih air)

jawaban : b

15. Termometer fahrenheit menunjukkan angka yang sama dengan dua kali angka yang ditunjukkan oleh termometer celcius pada suhu ...
a. 20 derajat C                                            b. 40 derajat C
c. 80 derajat C                                            d. 160 derajat C

pembahasan :

misalkan t derajat C = y, dari soal diketahui
maka 
jawaban : d

16. Suhu suatu zat menurut termometer celcius adalah 27 derajat C, maka menurut kelvin suhu itu sama dengan ...
a. 27 K                  b. 127 K                       c. 300 K                          d. 400 K

pembahasan :
dari soal diketahui 
maka

jawaban : c

17. Penunjukan skala termometer berikut yang mempunyai suhu paling rendah adalah ...
a. 0 K              b. 0 derajat C                       c. 0 derajat R                     d. 0 derajat F

pembahasan :
untuk mengetahui suhu yang paling rendah, maka skala suhu tersebut kita ubah ke skala celcius, maka :
(1) kelvin ke celcius
(2) reamur ke celcius
(3) fahreheit ke celcius
dengan demikian, suhu terendah adalah - 273 derajat C = 0 K

jawaban : a

18. Suhu suatu zat diukur oleh termometer fahrenheit adalah 55 derajat F. Jika diukur dengan termometer kelvin, maka suhu zat tersebut sebesar ...
a. 285,8 K                      b. 385,8 K                           c. 485,8 K                       d. 585,8 K

pembahasan :
dari soal diketahui :
maka kita cari dulu t derajat C :

dari rumus

jawaban : a

19. Suatu zat memiliki suhu sebesar 333 K, jika diukur dengan menggunakan termometer skala fahrenheit, maka suhu zat tersebut sebesar ...
a. 140 derajat F                                              b. 150 derajat F
c. 160 derajat F                                              d. 170 derajat F

pembahasan :
dari soal diketahui t K = 333
maka dengan menggunakan rumus :



jawaban : a

20. Sebagai titik patokan atas pada termometer fahrenheit adalah ...
a. suhu es yang sedang mencair
b. suhu es yang sedang mendidih
c. suhu badan orang sehat
d. campuran es dengan garam

pembahasan :
termometer fahrenheit memiliki ciri-ciri :
1. menggunakan air raksa sebagai pengisi termometer
2. patokan bawah (titik 0 derajat F) adalah suhu campuran es dan garam yang sedang mencair
3. patokan atas (titik 96 derajat F) adalah suhu tubuh orang sehat

jawaban : c

21. Sebagai titik awal pengukuran suhu badan manusia pada termometer klinik diambil suhu terendah badan manusia, yaitu ...
a. 25 derajat C                    
b. 27 derajat C
c. 35 derajat C
d. 42 derajat C

pembahasan :
suhu tubuh manusia memiliki titik terendah sebesar 35 derajat C dan suhu tertinggi 42 derajat C

jawaban : c

22. Alat untuk menyelidiki pemuaian berbagai zat padat adalah ...
a. barometer
b. bimetal
c. termometer
d. musschenbroek

pembahasan :
1. termometer adalah alat untuk mengukur tekanan udara luar
2. bimetal adalah dua keping logam yang angka muainya berbeda dikeling menjadi satu
3. termometer adalah alat untuk mengukur suhu
4. musschenbroek adalah alat untuk menyelidiki pemuaian berbagai zat padat

jawaban : d

23. Batang besi panjangnya 2 m pada suhu 20 derajat C. Setelah suhunya mencapai 80 derajat C, panjang batang besi menjadi ... (α = 0,000011/oC)
a. 2,0013 m
b. 2,0126 m
c. 2,0168 m
d. 2,0260 m

pembahasan :
Dari soal diketahui            lo  = 2 m
                                        to  = 20oC
                                        t    = 80oC
                                        α   = 0,000011/oC

maka :
Δt      = t - to
          = 80oC – 20oC
          = 60oC

Dan   l    = lo {1 + α Δt}
              = 2 {1 + (0,000011)(60)}
              = 2 (1 + 0,000660)
              = 2 (1,000660) = 2,00132 m

 jawaban : A

 24. Pada suhu 25 derajat C, panjang batang besi adalah 2 m. Berapakah panjang batang besi itu pada suhu 40 derajat C ? Jika :




a. 2,000 m
b. 2,00055 m
c. 2,0033 m
d. 0,0033 m

pembahasan :
dari soal diketahui :
maka :
jawaban : C

25. Apabila koefisien muai panjang suatu logam adalah :
sedangkan koefisien muai ruang (volume) logam tersebut adalah ...

pembahasan :
koefisien muai volume suatu zat padat adalah tiga kali koefisien muai panjangnya. Dengan demikian :

jawaban : d

26. Koefisien muai panjang suatu zat padat bergantung pada ...
a. panjang batang mula-mula
b. jenis zat padat
c. perubahan suhu
d. pertambahan panjang

pembahasan :
koefisien muai panjang berbagai zat padat diselidiki oleh alat yang disebut musschenbroek. Ternyata, untuk panjang yang sama dan perubahan suhu yang sama, pertambahan panjang berbagai zat padat berbeda-beda. Ini menunjukkan bahwa koefisien muai panjang suatu zat berbeda-beda, bergantung pada jenis zat padat.

jawaban : b

27. Angka muai gas besarnya sama dengan ...

pembahasan :
angka muai setiap jenis gas, menurut hasil pengamatan Gay Lussac, ternyata sama yaitu sebesar 

jawaban : a

28. Volume minyak tanah dalam sebuah wadah pada suhu 0 derajat C adalah 1 liter. JIka koefisien muai ruang minyak tanah , maka volume minyak tanah pada suhu 100 derajat C adalah ...
a. 1,000955 liter
b. 1,00955 liter
c. 1,0955 liter
d. 1,955 liter

pembahasan :
dari soal diketahui :
maka :
jawaban : c

29. Sebuah keping bimetal terbuat dari logam kuningan dan besi. Jika angka muai panjang kuningan lebih besar daripada besi, maka ketika bimetal dipanaskan ...
a. membengkok ke arah besi
b. membengkok ke arah kuningan
c. tetap lurus
d. menyusut

pembahasan :
jika keping bimetal dipanaskan, maka bimetal tersebut akan membengkok ke arah logam yang koefisien muainya terkecil. Karena kuningan memiliki koefisien muai panjang lebih besar daripada besi, maka bimetal akan membengkok ke arah besi

jawaban : a

30. Berikut adalah cara mengatasi masalah yang ditimbulkan oleh pemuaian, kecuali ...
a. membuat celah pada sambungan rel kereta api
b. membuat celah pada sambungan jembatan
c. membuat keping bimetal pada saklar otomatis
d. membuat ukuran bingkai jendela lebih besar dari kacanya

pembahasan :
pada siang hari, ketika panas terik, semua zat akan memuai. Seandainya sambungan rel atau jembatan tidak diberi celah, maka rel atau jembatan akan melengkung. Demikian, pula pada pemasangan kaca jendela. Apabila bingkai tepat sama dengan ukuran kacanya, maka tidak ada ruang tambahan ketika memuai. Ini akan mengakibatkan kaca retak. Sementara itu, membuat keping bimetal pada saklar otomatis tidak termasuk mengatasi masalah yang ditimbulkan oleh pemuaian, tetapi justru memanfaatkan peristiwa pemuaian

jawaban : c

31. Jika suatu zat dipanaskan sehingga mengalami kenaikan suhu 1 derajat C, maka zat yang memuai terbesar adalah ...
a. zat padat
b. zat cair
c. gas
d. tidak dapat ditentukan

pembahasan :
untuk kenaikan suhu yang sama, pemuaian suatu zat bergantung pada volume mula-mula dan koefisien muai ruang zat tersebut. Karena tidak diketahui volume zat mula-mula, maka pemuaian zat tersebut tidak dapat ditentukan

jawaban : d

32. Berikut ini pemanfaatan pemuaian dalam kehidupan sehari-hari, kecuali ...
a. pemasangan jembatan besi
b. pengelingan pelat logam
c. memasang roda pada ban baja sebuah lokomotif
d. keping bimetal

pembahasan :
pemanfaatan pemuaian dalam kehidupan sehari-hari antara lain :
- pengelingan pelat logam
- keping bimetal
- memasang roda pada ban baja sebuah lokomotif

jawaban : a

33. Alat yang tidak memanfaatkan bimetal adalah ...
a. termometer
b. saklar lampu
c. termostat
d. lampu tanda arah mobil

pembahasan :
termometer, secara umum tidak memanfaatkan bimetal, tetapi mempergunakan zat cair sebagai penigisi tabung termometer

jawaban : a

34. Supaya kaca pada filamen lampu pijar tidak pecah ketika dinyalakan, maka harus dibuat dari bahan gelas yang mempunyai ...
a. koefisien muai ruang besar
b. koefisen muai ruang kecil
c. massa jenis besar
d. massa jenis kecil

pembahasan :
pada saat lampu pijar menyala maka lampu akan panas. Udara yang berada dalam lampu akan memuai. Agar kaca tidak pecah karena pemuaian gas, maka kaca harus memiliki koefisien muai ruang yang besar

jawaban : a

35. Pemasangan kawat jaringan listrik tidak terlalu tegang. Hal ini dilakukan agar ...
a. tidak putus ketika panas
b. tidak putus ketika dingin
c. melengkung ketika panas
d. ada kesempatan pemuaian

pembahasan :
kawat jaringan listrik atau telepon dibiarkan kendor ketika panas. ini bertujuan agar ketika dingin, penyusutan kawat tidak mengakibatkan tali putus karena terlalu tegang

jawaban : b


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QUANTITIES, UNITS, AND MEASUREMENT

        After learning this chapter, we are expected to be able to group physical quantities and their units into basic quantities and derived quantities, as well as measure physical quantities by using standard units and nonstandard units.                     
         Before we learn, it will be better if you first we know what physics is. Certainly in elementary school we have learned the things which relate to physics in science. Physics is included into science, because science covers physics, chemistry, biology, astronomy, and geology. Etymologically, Indonesian word “Fisika” comes from the English word “physics”, while physics is derived from the word physikos meaning natural philosophy. As the result, physics is a science dealing with nature phenomena and the interaction of those natural phenomena which are expressed in mater and energy.                    
       In everyday life many activities corresponding to physics, for example measuring the length of wood, measuring body height, weighing mass or weight, measuring the length and width of land that will be built house and so on. Those activities are closely related to physical concept concerning with the measurement, quantities, and units.            
      In this chapter we will study quantities, units, and measurement covering the following topics :
1.      Definition of quantities, units, and measurement
2.      Basic quantities
3.      Derived quantities
A.      Definition of quantities, units, and measurement
    In everyday life, certainly we often hear the terminologies such as length, width, time, temperature, and so on. Those terminologies are included into quantities. In physics, quantities are very closely related to measurement. Meanwhile, the measurement has very important role in physics, moreover physics is not complete without the measurement of physical quantities.To more understand the definition of measurement, quantities, and units, let’s consider the following examples :
1.      When we go to a shop to buy flour  of 3 kg as stuff to make cakes, we will see the shopkeeper               do a measurement by using a balance, so it is obtained flour of 3 kg according to what we need.
2.      When we measure the length of the desk by using our span, after the measurement is done, obviously  span.

           The two examples above show the activities of measurement, that is the measurement of the amount of flour by using the balance and the measurement of the length of the desk by using the span. By the result of measurement in those two examples above, there are obtained the mass of flour is 3 kg and the length of desk is 8 spans. The number 3 shows the value of mass quantity and kg shows the value of length quantity and span shows the unit of the length quantity. By the information above, we can define quantities, units, and measurement. Meanwhile, the definition of quantities, units, and measurement in physics can be expressed as follows.                 
           Quantities are everything that can be measured, has value that can be expressed by numbers, and has the certain units.                          
           Units are a statement that explains the meaning of a quantity. Measurement is a process of comparing something measured with another as measures made as a standard. In other words, measurement is the process of comparing a quantity with another quantity which is used as unit.In the table below there are shown several examples of quantities which have their own value and units.

Quantities
value
Units
length
25
Meter
mass
3
Kilogram
time
45
Second

B.  Basic Quantities
           Quantities which are usually used in physics are differentiated into two, those are basic quantities and derived quantities. Basic quantities are quantities the units of which are predetermined and they are not derived from another quantities. Basic quantities consist of seven quantities, those are as shown in the table below. 
No
Basic quantities
Units name
Units symbol
1
Length
Meter
m
2
Mass
Kilogram
kg
3
Time
Second
s
4
Electric current
Ampere
A
5
Temperature
Kelvin
K
6
Luminous intensity
Candela
Cd
7
The amount of substance
mole
Mol

         Actually, in many regions on the earth there are still used various kinds of units for a quantity. For example, in measuring length, some using the units of hasta, span, feet, step and so on. It causes the difference in measurement result. That’s why those units cannot be valid internationally. Units which are not acknowledged internationally are called nonstandard units. Hence, it is necessary to be determined a unit system that is valid internationally functioning as standard units (or also called fundamental units).      
      In 1960, some scientists organized international conference which agreed standard units called International System Units (SI). This system replaces all of another systems found in the countries which use own numeric system. Metric system agreed using meter for length unit, kilogram for mass, and second for time. International system units by using basic units of meter, kilogram, and second (mks). Meanwhile another units the value of which are smaller and often used are cgs system units are : centimeter as the unit of length, gram as the unit of mass, and second as the unit of time.      
         Besides that, there are another unit systems that still widely used in several countries, those are British system units or fps system, among others, are as follows : the unit of length is expressed in feet, the unit of mass is expressed in pound, the unit of time is expressed in second.  
No
quantities
mks units
cgs units
British units
1
Length
m
cm
feet (ft)
2
Mass
kg
g
Pound (lb)
3
Time
s
s
Second (s)

Equivalence among mks, cgs, and British units are as follows :
1 kg = 1000 g1 m = 100 cm1 feet = 0,3048 m
1.      Length   
          Length is the distance between two points in a space. According to SI units, the length quantity is expressed in meter. It is necessary to be known, that width, height, distance, depth, circumference, and diameter are also length quantities.
              Before the agreement in using SI, the first international standard of length unit was a bar made of platinum-iridium alloy called standard meter. Nowadays, the device is stored in The International                  
              Bureau of Weights and Measures Paris, France. Below is a picture of a standard meter :

The use of this has several difficulties are as follows :
a.       It is easily to be broken and it is difficult to be remade
b.      The accuracy of its measurement is not relevant anymore for modern science and technology.
         To solve that problem, in 1990 physicists organized general conference about Weight and Measure. In the conference there was agreed that the length of 1 meter is equal to 1,650,763.73 times of the wavelengths of reddish-orange light emission from Krypton-86 (symbolized by Kr-86) in a vacuum, the accuracy level of which is higher than the bar of platinum-iridium alloy.
           In 1983, meter standard was reconverted to be one meter is equal to the distance traveled by light in a vacuum for 1/299,792,458 seconds. Another length units can use the multiplication of meter unit. For example are as follows :1 km = 1000 m = 10^3 m1 hm = 100 m = 10^2 m1 dam = 10 m = 10^11 dm = (1/10) m = 10^-1 m1 cm = (1/100) m = 10^-2 m1 mm = (1/1000) m = 10^-3 m
There are several kinds of measuring devices used to measure the quantity of length, among others, are as follows :
-          Ruler
We certainly often see or moreover use a ruler to measure something, such as for measuring the length of the desk. Commonly, the ruler uses cm or mm scale with accuracy of 0.1 cm or 1 mm. Below is picture of ruler :

      A vernier caliper has two main parts, namely outer jaw to measure thickness, such as the thickness of metal plate, and inner jaw part to measure the diameter of inner part of an object, for example the inner diameter of a tube and the inner diameter of the ring. The accuracy of the vernier caliper reaches 0.1 mm.      
       By the figure below, it looks that in a vernier caliper there are found two jaws, namely fixed jaw and sliding jaw. The fixed jaw has length scale which is called main scale, while the sliding jaw has short scale, which is called vernier scale. 

 -         Screw micrometers
                A screw micrometer has accuracy until 0.01 mm. The screw micrometer is usually used to measure tiny or small objects, such as the diameter of a wire and the thickness of paper. The screw micrometer has two scales, those are main scale and vernier scale, such as scales found in Vernier Calipers. 

2.     Mass
               The mass of the body is the amount of matter contained by the body. According to SI units, the unit of mass is kilogram (kg). In everyday life, we often use the terminology weight. For example, the weight of Usman’s body is 55 kg. According to physics, weight is the force experienced by a body which has mass because of gravity. According to the definition, the weight of the body in different places may be different depending on the magnitude of the gravity in that place.
          Mass standard of one kilogram in SI is fixed to be equal to the mass of platinum-iridium                   cylinder stored in International Bureau of Weight and Measures in Paris, France. This is the                   picture of platinum-iridium cylinder, 

Another mass units can be derived from kilogram unit as follows,
                   1 kilogram (kg) = 10 hectogram (hg) = 1000 g                   
                   1 g = 100 cg = 1000 mg                   
                   1 quintal = 100 kg                   
                   1 ton = 10 quintal = 1000 kg

Measuring device used to measure mass quantity is balances. Several kinds of balances are as                 follows :
-          Market balance
              Perhaps we have ever gone to the market with our mother to buy everyday needs such as sugar, oil, and vegetables. After our mother has chosen the food stuff required, the seller will weight to measure the mass of the food stuff according to the needs of our mother by using the balance. The balance which is often found in the markets is called the market balance, the picture shown below :

 -          Electronic balance
           An electronic balance has a screen which will show the value of the mass of the body measured automatically without need the weights of scale. The electronic balance is operated by using electrical power. Below is the picture of electronic balance :
 
-          Arm balance
             There are several kinds of arm balance i.e. two armed balance, three armed balance, and four armed balance. The working procedure of two armed balance is equal to market balance. Meanwhile, the working procedure of four armed balance is by regulating sliding load found in the base of the balance, so scale points, to the number zero when there is no yet the body to be measured. Put the body that will be measured its mass on the balance plate hanging at the short arm of the balance to the right. Then, make balance by sliding load to the most correct position. After that, read the mass of that body according to the scale pointer. For example, from the measurement result there is obtained the balance of the body when sliding load in the first bar shows the number of 100 grams, the second shows the number of 30 grams, the third shows the number of 7 grams, and the fourth shows the number of 0.3 grams, the mass of the body is 100 + 30 + 7 + 0.3 = 137.3 grams. Below is the picture of four arm balance,

3.      Time
                 Time unit in SI expressed in second. In the beginning, 1 second is defined as 1/86,400 of average day in the earth’s rotation. But, the eart's rotation period from year to year changes, so the measure of second become not precise. In 1967, physicist fixed that 1 second is equal to the time required by the cesium-133 atom to make vibration of 9,192,631,770 times. Below is the picture of Cesium atom clock,


Another time units are the multiplication of second unit.
1 ms = (1/1000) s = 0,001 s
1 mikro s = (1/1000000) s = 0,000001 s 

 Meanwhile time units usually used everyday are as follows :
1 minute = 60 s
1 hour = 60 x 60 s = 3600 s
1 day = 24 x 3600 s = 86400 s

          The time measuring device usually used in ancient were hourglass and sundial. Nowadays, the devices usually used as time measurer are watch and stopwatch. Below is the picture of several instrument of time measurement :
 

a. Watch
    Commonly, watches have three hands, those are hour hand, minute hand, and second hand.

b. Stopwatch
             Stopwatch is usually used in a laboratory or in sport activities that is to measure time interval of an event that activities. There is a stopwatch using hands to show its time, but there is also a digital stopwatch. 

 C. Derived Quantities
                Derived quantities are quantities derived from basic quantities. In the table there are shown the examples of derived quantities with their units.



1. Area
                  Area is derived quantity which is obtained by multiplying two length quantities. For example we will calculate the area of rectangle. 

Area = length x width
= length quality x length quantity
= m x m
= m^2


2. Volume
                   Volume is the number of spaces used by a body. Similar to area, volume is also derived of basic quantities, that is the product of three length quantities. Solids which have uniform shape such as cube, cuboid, sphere, and tube their volume can be calculated by using certain formula. (remember mathematics). Meanwhile solids which have nonuniform shape such as stone, its volume can be calculated directly. The measurement of its volume is done by using a measuring glass. What is the method?

                     The method to measure the volume of nonuniform solids can be done as in the following example :
a. fill the measuring glass with water about 200 mL. It means the initial is 200 mL.
b. then, put a stone that will be measured into the measuring glass. For example the volume of water and the
  stone becomes 300 mL. This volume is called the final volume.
c. subtract the final volume by the initial volume, so the difference is the volume of the stone
mengukur volume batu dengan gelas ukur

So, the volume of stone = final volume - initial volume
                                    = 300 mL - 200 mL
                                    = 100 mL = 100 cm^3 = (100) / (1000000) = 0,0001 m^3

D. Working in the laboratory
                     In learning physics, besides learn theory in a class you need also to do several experiment or practicums in a laboratory to apply or prove the theories obtained in the class. Besides that, by doing practicum, you will get valuable experience and joyful impression in learning physics.

1. Laboratory equipment
                In a laboratory there are found devices and materials to do a practicum. Devices usually found in a physics laboratory are balances, thermometer, stopwacth, ruler, vernier caliper, glasess, glass jars, bunsen burner, reaction tubes, and so on. Meanwhile the materials usually found in the laboratory are chemicals.
beaker glass

2. Working safety
                 Practicum in a laboratory closely relates to devices and materials which sometime can cause any accident if it is done by inappropiate method. For example, when you use spirit burner or bunsen burner you must be careful because spirit is flammable, so don't make it spill on a desk and the connecting tube of the gas flow in bunsen must be attached strongly, do not to be released. Hence, it is necessary to be considered the use of those devices and materials, so not happen any accident when doing practicum, because working safety in the laboratory is an important factor for everyone. Besides that, it is necessary also to understand the meaning of symbols or sign which are usually written in the package of chemicals or the certain devices, among others, are as follows :

  

         The things that must be considered in doing practicum in a laboratory are as in the below :
  1. plan the experiment which will be done before starting the practicum
  2. prepare the things required and what must be considered before entering the laboratory such as a note book, the kind of experiment, the kind of materials, the kind if devices, and the methods to remove the waste of the experiment remain
  3.  master the working procedure and ask your theacer if you have any doubt or do not know about something
  4. wear a coat and goggle while you are doing an activity. They are useful for protecting our skin, eyes, and other body parts from a harmful chemical substance
  5. do not wear a sandal or opened shoes or highly sole shoes
  6. fit your hair if your hair is long
  7. do not eat or drink while you are in the laboratory
  8. keep the cleaness of a practicum desk. If the practicum desk is wet, immediately dry it by using a napkin
  9. avoid direct contact with chemical stuffs
  10. do not smell a chemical substance directly from a bottle nozzle
  11. make sure the gas tap is not leak when using bunsen
  12. make sure the water and gas taps are always in closed position before and after practicum is finished
  13. do not work alone in the laboratory, minimally there is a theacher observing
  14. do not play with a laboratory equipment and chemical stuff
  15. do not make mistake among friends
  16. if your body is splashed by a certain chemical substance, wash it with water as much as possible
  17. if accident happens, immediately contact paramedics
  18. devices used in practicum must be kept as well as possible, do not until be broken

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