fisika aplikasi

1. Fisika Aplikasi
Sifat Fluida
2022

2. Tujuan pembelajaran:
• Mahasiswa mampu menjelaskan sifat-sifat
fluida.

3. Topik
• Properties of Fluids
– Density
– Specific Weight
– Specific Gravity
– Viscosity
– Newtonian fluids
• Hydrostatic Pressure
– Vapour Pressure
– Atmospheric Pressure
– Pressure Intensity
• Buoyancy

4. Fluida
• Material/ bahan/ zat yang dapat mengalir,
dalam wujud gas maupun cairan.
• Gas: tekanan dan volume mengikuti hukum
gas ideal.
• Liquid: tekanan tidak banyak merubah
volume.

5. Properties of Fluids
•Density
•Specific Weight
•Specific Gravity
•Viscosity
•Newtonian fluids

6. Density

7. Specific Weight

8. Specific Gravity
• also called relative density, ratio of the density
of a substance to that of a standard substance.

9. Specific Gravity
• The usual standard of comparison for solids
and liquids is water at 4 °C (39.2 °F), which
has a density of 1.0 kg per litre (62.4 pounds
per cubic foot).
• Gases are commonly compared with dry air,
which has a density of 1.29 grams per litre
(1.29 ounces per cubic foot) under so-called
standard conditions (0 °C and a pressure of 1
standard atmosphere).

10. Specific Gravity
Contoh:

11. Viscosity
• Viskositas adalah ukuran kekentalan fluida
yang menggambarkan resistensi fluida untuk
bergerak atau terdeformasi.

12. Viscosity

13. Viscosity
F = gaya yang bekerja (N)
A = luas keping yang bersentuhan dengan fluida (m2)
v = kelajuan fluida
L = jarak antar keping
η = koefisien viskositas Kg m-1 s-1 atau pascal.second

14. Newtonian Fluid
• Viskositas konstan, tidak
tergantung kecepatan.
• Kurva linier
• Slope: konstan

15. Hydrostatic Pressure
•Vapour Pressure
•Atmospheric Pressure
•Pressure Intensity

16. Pressure
A fluid in a container presses with an outward force
against the walls of that container. The pressure is
defined as the ratio of the force to the area on which the
force is exerted.
The SI units of pressure are N/m2, also defined as the
pascal, where 1 pascal = 1 Pa = 1 N/m2.
Other units:
1 atm =
1 mmHg = 133 Pa
1 kPa = 103 Pa
1 psi = 6890 Pa

18. Atmospheric Pressure
The global average
sea-level pressure is
Pa, or 1 atm.

19. Pressure Intensity
• is the magnitude of pressure at a point.
• can be either Guage pressure or Vacuum
pressure.
• Satuan: Pascal

20. Contoh:
Pressure intensity at a point in a fluid at rest is 4
N/cm^2. The corresponding height of water
would be (assume g = 10 m/s^2)
P=ρ.g.h
4.10^4 N/m^2 = 1000.10.h
h= 4 m

21. Contoh:
P=ρ.g.h=(13,6.10^3 kg/m^3).(10m/s^2).(0,12 m)
=16320 pascal

22. Buoyancy
Buoyancy atau Gaya apung adalah gaya ke atas
yang dikerjakan oleh fluida yang melawan berat
dari benda yang direndam.

25. Contoh:
Sebuah benda memiliki massa sebesar 50 kg
ketika berada di udara. Kemudian benda
tersebut diukur di dalam air dan hasil
pengukurannya sebesar 25 kg. Jika benda
tersebut berada seluruhnya di dalam air dengan
massa jenis sebesar 1000 kg/m3, volume benda
tersebut adalah....

26. • F1 = m1 x g = 50 x 10 = 500 N
• F2 = m2 x g = 25 x 10 = 250 N
• Fa = F1 - F2 = 500 – 250 = 250 N