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(4) PHY08221-Biofisika-5 Fluida Statis

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materi kuliah biofisika pak Wihantoro, M.Sc

Text of (4) PHY08221-Biofisika-5 Fluida Statis

KULIAH 5Pokok BahasanSub Bahasan


BIO-MEKANIKA (FLUIDA)Fluida Statika: Fenomena fisika hayati pada fluida statis (diam) Fluida Dinamika: Fenomena fisika hayati pada fluida dinamis (mengalir)

Tujuan Pembelajaran, mahasiswa mampu- menerapkan konsep tegangan permukaan dalam mengkaji fenomena bergeraknya mahluk hidup di atas permukaan air - menerapkan konsep perbedaan tekanan dan persamaan Bernouli dalam mengkaji aliran darah dalam tubuh

PUSTAKA RUJUKANKrane, Joseph W and Morton M Sternheim (1978). Life Science Physics. John Wiley and Sons


Besaran fisis fluida: Massa jenis Massa Jenis (densitas) dan tekanan suhu


Nilai -zat bergantung pada

Pressure in a fluid At any particular depth, the pressure is constant throughout a fluid. Review Pengertian Tek Hidrostatik


Pressure= P =


P cairan = P darah

Fdorong Atabung

= Pdarah

Fdorong =P darah A tabung

Pascal's Law Variation of static pressure with depth

po = 1.013x105 Pa at sea level p increases with depth by an amount mgh. NOTE that an increase in pressure applied to an enclosed fluid is transmitted undiminished to every point in the fluid (including the walls of the container)- Pascals Principle

Variasi Tekanan: INFUS

Perbedaan tekanan antara cairan di BOTOL dan cairan yang masuk ke dalam pembuluh darah pasien dapat dihitung dari tekanan total, yaitu:P =P gh 0 + P = gh P P gh 0 =

A collapsible plastic bag contains a glucose solution. If the average gauge pressure in the artery is 1.33x104 Pa, what must be the minimum height h of the bag in order to infuse glucose into the artery? Assume that the specific gravity of the solution is 1.02.

Variation of Pressure with Depth In equilibrium, all points at the same depth must be at the same pressure. Otherwise a net force would be applied and the fluid would accelerate. Tekanan bekerja di setiap titik arah gaya dalam posisi tegak lurus dan tidak memperhatikan bentuk benda, total massa ataupun luasan permukaan cairan.

Tekanan Hidrostatik: Penyebab kejang otot?

Pressure Measurements

open-tube manometer


Note that P = absolute (true) 1 atm. pressure equal to a 0.76 m column of pressure inside the bulb. P-P0 is the mercury at T=0C and g=9.80665 m s-2. gauge pressure, the pressure that is added to the atmospheric pressure to equal P.

Prinsip kerja alat ukur tekanan darah: sphygnomanometer Tekanan di titik A sama dengan tekanan di titik 1, tekanan di titik 2 sama dengan tekanan di titik 1 + 1gh1. Tekanan di titik 2 sama dengan tekanan di titik 3, yaitu 2gh2 Berdasarkan persamaan tekanan di titik 2 dan titik 3, maka didapat :

PA + 1 gh1 = 2 gh2Jika A diisi udara, maka umumnya tekanan 1gh1 dapat diabaikan, karena massa jenis udara sangat kecil sehingga p2 pA.PA = 2 gh2

bilangan tekanan darah

Blood pressure is recorded as two numbers: the top number is called systolic pressure and the bottom number is called diastolic pressure.

Tabel bunyi detak tensimeter: Korotkov sounds dapat dilihat di

Tekanan darah normal dalam keadaan istirahat

Normal blood pressures are said to range from 100/60 mmHg to 150/90 mmHg.Some 'average' blood pressures relating to age (year) in mmHg Age New-born 10 20 40 60 Systoli Diastoli c c 80 103 120 126 135 46 70 80 84 89

Ideal resting rate:range.html

Classification of blood pressure for adultsCategory Hypotension Normal Prehypertension Stage 1 Hypertension Stage 2 Hypertension systolic, mmHg < 90 90 119 120 139 140 159 160 diastolic, mmHg < 60 60 79 80 89 90 99 100

Chobanian AV, Bakris GL, Black HR, et al (December 2003). "Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure". Hypertension 42 (6): 120652. doi:10.1161/01.HYP.0000107251.49515.c2. PMID 14656957. Diseases and Conditions Index - Hypotension". National Heart Lung and Blood Institute. September 2008. Retrieved 2008-09-16.

Heart Rates for Various Mammals (beats/mi n)

Generally speaking, the larger the animal, the slower its resting heart rate. Camels and bats represent the two extremes of the scale, with most other mammals falling somewhere in between.

Whale 20 Cat 150

Horse 45 Hamster 330

Human 70

Blood pressureA measure of how hard blood is pressing against artery walls.


Blood pressure is the amount of pressure exerted on the walls of the arteries as the blood moves through them. Blood pressure is measured in terms of the millimeters column of mercury (in mmHg) that could be supported by the pressure inside the arteries at two times: maximum thrust by the heart, and when the heart is relaxed. These are normally about 120 mm and 80 mm, respectively. Recent medical guidelines suggest that the familiar old normal 120/80 values are too high, and that somewhat lower values are desired!

Titik-titik arteri (simpul); lokasi tekanan darah terdeteksi dengan kuat

Bed rest; relaxing your heart

Tekanan darah: selisih ketinggianEstimate the amount by which blood pressure changes in an actuary in the foot P2 and in the aorta P1 when the person is lying down and standing up. Take density of blood = 1060kg/m3Lying down P2 P gh = 0 Pa 1 = s tan ding P2 P 10 4 Pa 1 =1060 * 9.8 *1.35 =1.4

FLUIDA STATIKA: Tegangan PermukaanDefinisi Tegangan Permukaan The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension.

Note that depends on temperature. At higher T, the molecules are not as tightly bound together. You can also alter the surface tension of fluids using additives. If the surface becomes curved as in the picture below, it may support a weight. This is illustrated clearly below Surface tension is actually defined the force per unit length in a surface needed hold the surface together: as to

If the weight vertically for the needle: of the needle is W, resolve


Tegangan Permukaan yang dialami seranggaThe base of an insect's leg is approximately spherical in shape with a radius of about 2.0 10-5 m. The mass of the insect is 3.00 10-6 kg and is supported equally by six legs. Calculate the contact angle as shown in the diagram. The coefficient of surface tension is 0.072 N/m.

SOLUSI radius of insect leg = R = 2.0 10-5 m mass of insect = m = 3.00 10-6 kg insect supported by 6 legs coefficient of surface tension = = 0.072 N.m-1 contact angle = = ? Assume the surface tension acts around the circle of radius R, where R is the radius of a leg. This is not accurate since the radius of the surface depression is not precisely the radius of the leg. Equilibrium (2) (FT cos ) = FG ; FT = (2 R) FG = m g / 6 (2 R) cos = m g / 6 cos = (m g) / {(12 R) } cos = (3.00 10-6 )(9.8) / {(12)(2.0 10-5)(0.072 )} cos = 0.54157 = 57 If cos 1 or 90 surface tension would not support insect.

Pressure and Blood Flow

The higher the pressure exerted by the heart, the faster blood will flow. Another factor which controls the blood flow rate is the resistance of the blood vessels to blood flow.

flow rate of blood in aorta?Calculate the flow rate of blood (of density 0.722 g/cm3) in an aorta with a cross-sectional area of 2.67 cm2 if the flow speed is 36.6 cm/s. Answer in units of g/s. Assume the aorta branches to form a large number of capillaries with a combined cross-sectional area of 1820 cm^2. What is the flow speed in the capillaries? Answer in units of cm/s. use the equation m = p * v * A = 0.722 * 36.6 * 2.67 = 70.555284 g/s. for the second question, use conservation of flow rate: p v A = p v a, 70.555 = 0.722 * v * 1820, v = 0.0536931905 cm/s