BAB ISATUAN DALAM KETEKNIKAN

1.1. PENGERTIAN SATUAN1.2. SISTEM SATUAN

1.3. KONVERSI SATUAN

BAB ISATUAN DALAM KETEKNIKAN

1.1. Pengertian Satuan Satuan : Ukuran yang digunakan untuk menunjukkan hasil pengukuran atau observasi yang bersifat kuantitatif.

Dimensi : Simbol yang digunakan untuk menunjukkan hasil suatu pengukuran atau obsevasi.

1.2. Sistem Satuan Sistem satuan dalam terdiri dari :

1. Sistem Satuan Metrik (SI) a. Sistem satuan CGS (Cm-Gram-

Detik)b. Sistem satuan MKS (Meter-Kg-Detik)

2. Sistem Satuan British (Inggeris)a. Sistem satuan fps(Foot-Pound-Second)b. Sistem satuan keteknikan (Foot-Pound mass-Second)c. Sistem satuan Gravitasional (Foot-Slug-Second)

Satuan Dasar Table 1. SI Base Units (MKS)

Source :

Base SI Base UnitQuantity Name Symbol

Length meter mMass kilogram kgTime second sThermodinamic temperature kelvin KElectric current amper ALight intensity candela cdAmount of substance mole molForce newton N

gc kg-m/newton second2 kg-m/N s2

Table 2. SI Base Units (CGS)Base SI Base Unit

Quantity Name SymbolLength centimeter cmMass gram gTime second sThermodinamic temperature Degree celsius °CElectric current amper ALight intensity candela cdAmount of substance mole molForce dyne d

gc g-cm/dyne second2 g-cm/d s2

Source :

Table 3. British System Units

Source :

Base British Base UnitQuantity Name Symbol

Length foot ftMass pound-mass lbm

Time second sThermodinamic temperature Fahrenheit °FElectric current amper ALight intensity candela cdAmount of substance mole molForce pound-force lbf

gcpound-mass foot/pound-

force second2

lbm-ft/lbf s2

Dimensions and Units of Some Commonly used Quantities in Transport Phenomena

Quantity Dimension Unit (SI)Mass M kilogram (kg)

Length L meter (m)Time second (s)

Temperature T kelvin (K)Velocity L-1 (m/s)

Acceleration L-2 (m/s2)Force ML-2 (kg m/s2)

Energy ML2-2 (kg m2/s2) ; (Newton)Work ML2-2 (kg m2/s2) ; (Newton)Heat ML2-2 (kg m2/s2) ; (Newton)

Pressure ML-1-2 (kg/m/s2) ; (Pascal)Stress ML-1-2 (kg/m/s2) ; (Pascal)

Elasticity ML-1-2 (kg/m/s2) ; (Pascal)Viscosity ML-1-1 (kg/m/s) ; (Poise)

Diffusivity L2-1 (m2 s-1)Thermal conductivity ML-3T-1 (kg m s-3 K-1)

Spesific L2-2T-1 (m2 s-2 K-1) ; (J/kg/K)

Table 4.  Examples of SI derived units

Sumber : Anonimouos, 2012

Derived quantity Name Symbolarea square meter m2

volume cubic meter m3

speed, velocity meter per second m/sacceleration meter per second squared   m/s2

wave number reciprocal meter m-1

mass density kilogram per cubic meter kg/m3

specific volume cubic meter per kilogram m3/kgcurrent density ampere per square meter A/m2

magnetic field strength   ampere per meter A/mamount-of-substance

concentration mole per cubic meter mol/m3

luminance candela per square meter cd/m2

mass fractionkilogram per kilogram, which

may be represented by the number 1

kg/kg = 1

1.3. Konversi Satuan Tujuannya :Mengkonversi satu set unit pada

fungsi atau persamaan ke satu set unit lainnya sehingga memiliki unit yang sama dalam suatu persamaan. Misal : 1. 1 foot = 0,3048 m ; 1 m = 3,2808 feet2. 1 pound = 0,4536 kg; 1 kg = 2,2046 lb 3. 1hp = 550ft lbf/s4. 1 lbf = 32,174 lb-ft/s2

5. 1hp = 550 x 32,174 lb ft2/s2

6. 1hp = (550 x 32,174 x 0,4536 x (0,3048)2) J = 745.711 J7. 1dyne = 1g cm/s2 = (10-3 x 10-2) kg m/s2 = 10-5 N8. T(oC) = T (K) – 273,16 ; T(oF) = T (K)/1.8 – 459.679. 1cal = 4,1840 J ; 1calIT = 4,1868 J 10. g = 9,81 m/s2 = 981 cm/s2 = 32,174 ft/s2

Contoh : Konversi 3 m berapa inchi = ?

Answer = 118 inchi

Konversi 3 m/s berapa m/hr = ?

Answer = 10.800 m/hr

? = 3.00 m 100 cm 1 in 1 m 2.54 cm

? = 3.00 m 60 s 60 min s min hr

How many milligrams are in a kilogram?1 kg = 1000 g 1 g = 1000 mg 1 kg x [1000 g/1 kg] x [ 1000 mg/g] = 106 mg

You have 1,5 pounds of gold. Find its volume in cm3 if the density of gold is 19,3 g/cm3.

How many liters of water would fill a container that measures 75.0 in3?

1 cm3

19.3 g 1.5 lb 1 kg

2.2 lb = 35 cm31000 g

1 kg

= 1.23 L75.0 in3 (2.54 cm)3

(1 in)3

1 L1000 cm3

Volume: 12 ft3 to Liters

1 g/cm3 = ……… lbm/cuft[1g/cm3][1lbm/453,6g][(2,54)3cm3/1in3][123in3/1ft3]= 62,4 lbm/ft3.

10-2 poise = ……… lbm/ft sec1 poise = 1 g/cm sec.[10-2g/cm sec][1 lbm/453,6 g][1 cm/0,0328 ft] = 6,72 x 10-4 lbm/ft sec.

T(OR) = T(OF) + 459,58T(OK) = T(OC) + 273,15

12 ft3 (12)3 in3 (2.54)3 cm3 (1)3 m3 1000 L (1)3 ft3 (1)3 in3 (100)3 cm3 1 m3

Konversi Satuan

Item Keteknikan Amerika

cm-gram-second (cgs)

Satuan Internasional

(SI)Panjang

(L) 1 foot (ft) 30,48 cm 0,3048 m

Masa (M)

1 pound-mass (lbm) 453,6 g 0,4536 kg

Waktu () 1 detik 1 detik 1 detikVolume

(V)1 cuft (ft3) 2,83 x 104 cu-cm

(cm3) 0,0283 cu-m (m3)

Gaya (F)

1 pound force (lbf)

4,448 x 105 dyne 4,448 Newton (N)

Energi 1 foot-pound (ft-lbf)

1,356 x 10-7 ergs (erg) 1,356 joule (J)

Tekanan 1 pound/sqft (lbf/ft2)

478,8 dyne/cm2 4,788 N/m2 atau Pa

Suhu (T) OF OC K

0.532

=

532 m = _______ km

NUMBER

UNITNUMBER

UNIT