Pengantar Biomekanika Dita Ayu Mayasari, ST., M.Biotech Biomedical Engineering Univ. Dian Nuswantoro
Pengantar BiomekanikaDita Ayu Mayasari, ST., M.Biotech
Biomedical Engineering
Univ. Dian Nuswantoro
Dasar-Dasar Biomekanika
What is Biomechanics?
Applies mechanical principles to the human body in order to understand the
mechanical influences on bone and joint health
(Kelleys and Firestein’s Textbook of Rheumatology 10th Ed, 2017)
Why should we learn about
biomechanics?
Biomechanics
Ergonomic Utility
Medical Rehabilitation
Forensic
Sports
Why should we learn about
biomechanics?
Elements of Biomechanics
Statics: Studying systems that are in equilibrium, either at rest or moving at a
constant velocity.
Dynamics: Studying systems that are in motion with acceleration and
deceleration.
Kinetics: Studying what causes motion, the forces and moments at work.
Kinematics: Describing the effect of forces on a system, motion patterns
including linear and angular changes in velocity over time. Position,
displacement, velocity, and acceleration are studied.
Biomechanical Principles
Basic biomechanics relies heavily on Newtonian mechanics
Newton’s First Law – Law of Inertia
Objects tend to resist changes in their state of motion.
Newton’s Second Law – Law of Acceleration
Links the kinematics of a body to its kinetics
Newton’s Third law – Law of Reaction
There is an equal and opposite reaction force for every action (force)
Force
Gravitation
Spring
R2=
GMFg
m
Fs = kx
FN
Ff = Fc
Normal
Friction
Vector
Has magnitude and direction
Vectors are similarly represented in three dimensions in terms of their i, j,
and k components
A set of forces may be combined into an equivalent force denoted the
resultant R
Vector multiplication consists of two distinct operations: the dot and cross
products
|A x B|= AB sin A ∙ B = AB cos
Penjumlahan & Pengurangan Vektor
Torque
Forces describe changes in linear motion – which means changes in velocities,
while torques describe how these same forces can change angular motion –
which means changes in angular velocities
τ = r × F
Momen Inersia
ukuran kelembaman suatu benda untuk berotasi terhadap porosnya
analog rotasi daripada massa
berperan dalam dinamika rotasi seperti massa dalam dinamika dasar, dan
menentukan hubungan antara momentum sudut dan kecepatan sudut, momen
gaya dan percepatan sudut, dan beberapa besaran lain
𝐼 = 𝑚
𝑟2 𝑑𝑚
Static Equilibrium
∑F = 0
∑M = 0
Contoh Masalah :
Diketahui:
Seseorang dengan berat 160 lb
menahan beban bola 10 lb dengan
siku menekuk 90 derajat
Hitung:
Gaya yang harus dihasilkan oleh
otot bisep (Fb)
Jawab:
Biotransportasi
Mekanika Fluida
Zat Alir cairan, gas
Fluida statis & dinamis
Hidrostatika
TEKANAN HIDROSTATIKA
dF
Pm = P0 + ρgh
𝑃 =𝑑𝐹
𝑑𝐴
m
h
po
Tekanan terukur
P = P0 + ρgh
P – P0 = ρgh
misal h = 80 mm, berarti tekanan gas dlm tabung 80 mmHg
Hukum Archimedes
Sebuah benda bila berada dalam zat cair akan mendapat gaya ke atas (B)
sebesar berat zat cair yang dipindahkan
F2 – F1 = B = ρzat cair g vbenda
F1
F2
Hidrodinamika
Laminer : memiliki garis arus sendiri-sendiri kerapatan dan kompresibilitas
sama
Turbulen : garis arusnya saling berpotongan dan kerapatannya tidak merata
Bilangan Reynold
𝑅 =𝜌𝑣𝐷
𝜂
V = kecepatan aliran
D = diameter pipa
𝜂 = koefisien viskositas
bila R < 2000 aliran laminer
R > 3000 aliran turbulen
Persamaan kontinuitas
volume zat cair yang mengalir perdetik di setiap titik adalah sama
Q1 = Q2 = Q3 …
A1V1 = A2V2 = A3V3 …
A : luas penampang pipa
V : kecepatan aliran
Persamaan Bernuolli
Latihan Soal
1. Seorang anak (ρ=0,98 g/cm2) berada dalam keadaan terapung dengan
sebagian tubuhnya berada dalam kolam. Berapa bagian tubuh yang berada di
dalam air?
2. Sebuah bola ditengahnyan berongga , rdalam=10 cm dan rrongga =8cm. Bila
berada dalam keadaan melayang dalam air maka tentukan massa jenis bola
tersebut.
Diketahui:
Seseorang dengan berat 150 lb
(berat kaki 0.061 dari berat total
tubuh)
Hitung:
W?