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FISIKA DASAR. By: Mohammad Faizun , S.T., M.Eng . Head of Manufacture System Laboratory Mechanical Engineering Department Universitas Islam Indonesia. Everything which can be MEASURED is quantity . 1. QUANTITY ( besaran ) and UNITS ( satuan ).
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FISIKA DASAR By: Mohammad Faizun, S.T., M.Eng. Head of Manufacture System Laboratory Mechanical Engineering Department Universitas Islam Indonesia
Everything which can be MEASURED is quantity. 1. QUANTITY (besaran) andUNITS (satuan) • From the picture below you can exactly say that line B is longer than line A. Paper D is narrower than paper C. • Length and Area are two examples of quantity. Quantity is the properties of matter which can be measured. A C D B
Fill in the empty cell on the table below! • “Everythingthat can be COUNTED is quantity”. Is this statement true? Why? • What is the difference between COUNTING (menghitung) and MEASURING (mengukur)?
Quantity without units is worthless. • We can differentiate two things or more by comparing their quantities for example: longer, narrower, lighter, colder, etc. But you still confused unless you tell exactly how big the quantities. So we need units. • For example: • 12 cm, 30 feet, 120 km. cm, feet, and km are examples of units for length quantity. • 12 gram, 30 pounds, 2 ton. Gram, pound, and ton are examples of units for mass quantity. • 5 second, second is an example of units for time.
Determine the quantity and the units in each information below if possible! • Ruddy is 1.75 meters tall. • Mr. Anton has five cars. • The mass of the book is 1 kg. • We need 4 litres of water a day. • I will stay here a month. • The speed of the car is 100 km/h.
QUANTITY (besaran) UNITS (satuan) MEASUREMENT (Pengukuran) Satuanadalahnilaitertentu yang disepakatidarisuatubesaran. Pengukuran: membandingkannilaibesarandengansatuannya. RESULT Value + unit 6 cm
There are two kinds of units: SI (Systéme International) units and non SI units. • SI units is Internationally accepted, means all people in all countries know that units. Non SI Units m k s Units SI Units c g s (gaussian)
It’s suggested to always use SI units. How are those SI units defined?
one meter In October 1983, the meter (1 m) was redefined as the distance traveled by light in vacuum during a time of 1/299 792 458 second. In effect, this latest definition establishes that the speed of light in vacuum is precisely 299 792 458 m per second. One meter that we use today is same with the definition. We use roll meter for example to measure length of the wood bar or others.
A B • one kilogram Mass is amount of matter in an object. To get better understanding please compare two cans filled in with different amount of marbles. Guess which can has more weight! Can A has marbles less than can B, 8 less than 16, right? So, can A has smaller mass than can B. The basic SI unit of mass, the kilogram (kg), is defined as the mass of a specific platinum–iridium alloy cylinder kept at the International Bureau of Weights and Measures at Sèvres, France. This mass standard was established in 1887 and has not been changed since that time because platinum–iridium is an unusually stable alloy (Fig. 1.5). We use arm balance to measure mass of something.
One Kilogram Standard Arm Balance Benarkahneracapegasbisadipakaiuntukmenghitungmassasebuahbendadimanasaja? Jelaskanalasannya!
one second The basic SI unit of time, the second (s), is defined as 9,192, 631,770 times the period of vibration of radiation from the cesium-133 atom.
In addition to the basic SI units of meter, kilogram, and second, we can also use other units, such as millimeters and nanoseconds, where the prefixes milli- and nano- denote various powers of ten.
2. BASIC QUANTITIES (besaranpokok) and ITS DERIVATION(besaranturunan) • Fundamentals or basic quantities is now believed as quantities that not derived from other quantities. Even they form other quantities.
10 cm 10 cm 10 cm Besaranturunan • Besaranturunanadalahbesaran yang terbentukdaribesaran-besaranpokok. • Contoh: Luas panjang x panjang, Volume panjang x panjang x panjang Beratmassa x panjang x waktu-2 Volume: 10 cm x 10 cm x 10 cm. : 1000 cm3.
SCALAR AND VECTOR QUANTITIES Basic Quantities scalar derivative vector Scalar quantity is one that has only value but no direction. Example: mass, length, time. All basic quantities are scalar quantities. Vector quantity is one that has both value and direction. Example: force, velocity, pressure, etc.
v = 10m/s 1 L B A See figure below! A. You know that the volume of cylinder is 1 liter. If you asked where is the direction of that volume you will not be able to answer, because volume doesn’t have direction. So, volume is scalar quantities. B shows that the velocity of the block is 10 m/s and the direction is rightward. Having velocity without direction is impossible.
QUESTIONS • What is the definitions of quantity? • Please fill in the table below!
Is it true that quantity has two kinds, SI and non SI? • Suppose that two quantities A and B have different dimensions. Determine which of the following arithmetic operations could be physically meaningful: (a) A-B (b) A/B (c) B+A (d) AB. • What are use of units? • Mention the differences between basic units and derived units! • Why are units very important for us? • Fill in the table below.
3. DIMENSIONAL ANALYSIS • The word dimension has a special meaning in physics. It usually denotes the physical nature of a quantity. Whether a distance is measured in the length unit feet or the length unit meters, it is still. • For example we will find the dimension for volume (V). = [L] x [L] x [L} = [L]3 So the dimension of volume is [L]3.
Example • Suppose we are told that the acceleration a of a particle moving with uniform speed v in a circle of radius r is proportional to some power of r, say rn, and some power of v, say vm. How can we determine the values of n and m? • Solution Let us take a to be where k is a dimensionless constant of proportionality. Knowing the dimensions of a, r, and v, we see that the dimensional equation must be
This dimensional equation is balanced under the conditions n + m = 1 m = 2 So, n = -1 Then we can write the acceleration expression as (in the next discussion about uniform circular motion we will see this formula)
Exercise: Please find the dimension of: a. Gravity (g) f. electrical force. b. Heat energy g. Power c. Pressure h. Electrical charge d. Electrical resistance i. Capacitance of Capacitor e. Spring constant (k) j. electron mass.
About the Author • Name : Mohammad Faizun, S.T., M.Eng. • Education : B.Eng., GadjahMada University (2003-2007) : M.Eng., University of Malaya (2009-2011). • Job : a. Production Engineer, BekaertStanwick (2007- 2009) b. Head of Manufacture System Laboratory, Islamic University of Indonesia (2011- now) c. Lecturer at Mechanical Engineering Dep. Islamic University of Indonesia (2011- now) • Expertise : Robotics, Electronics, Microcontroller, PLC, Computer Vision and Image Processing, and C++ Programming.