biomechanic @dokter budi

8/10/2019 Biomechanic @Dokter Budi

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Budi Santoso, dr

Bagian Fisiologi dan Fisika Medik

Fakultas Kedokteran Universitas Sriwijaya


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Pakaian sopan

no jeans,

no T-shirt,

no ketat, no sandal


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Mau belajar fisika lagi??

Inget Gerak lurus beraturan (GLB), GJB ??????


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Describe:

What is biomechanics?

Laws of motionLevers & their classification

Equilibrium, balance, & stability

Factors influencing balance

Mekanika material


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Perhatikan gambar dibawah

Normal human body

Its physically impossible for you to lick your elbow.


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Bio= life; Mechanics= physical actions

Statics: form of mechanics that analyzes

systems in constant state of motion Could be no movement at all Could be constant velocity with no acceleration

Dynamics: form of mechanics that analyzessystems in motion and accelerating


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Anatomical kinesiology is the what

Muscle origins, insertions, and actions

Biomechanics is the how

Mechanical principles that dictate the manner those

muscles work


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HUMAN CHARACTERISTICS: Skeleton

Muscles

Tendons Ligaments

Joints

Neural command

Reflexes

- Levers

- Actuators

- Joints

- Pulleys

- Springs

- Dampers

MACHINE CHARACTERISTICS


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Newton 1 law of Inertia

Newton 2 law of Acceleration

Newton 3 law of Reaction


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Selama tidak ada resultan gaya yang bekerja pada

sebuah benda maka benda tersebut akan selalu pada

keadaannya, yaitu benda yang diam akan selalu diam

dan benda yang bergerak akan bergerak dengankecepatan konstan.

S F = 0 a = 0

Hukum

KelembamanSistem Inersial


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Inertia

Kecenderungan tubuh untuk bertahanpada kondisi/posisi tertentu

semakin besar tubuh inertia

Implications for sport movement

Decreased mass USUALLY means you

are easier to move (less inertia)


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Percepatan pada sebuah benda sebanding dengan

resultan gaya yang bekerja pada benda tersebut

Fa

aF .m

Satuan Gaya : newton (N)2-smkg1N1 2scmg1dyne1

1 N = 105 dyne


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Gaya sebesar 1 Newton diartikan sebagai besarnya gaya yang bila

dikerjakan pada benda bermassa 1 kilogram akan menghasilkan

percepatan 1 meter per sekon kuadrat.

Impulse

Ft = m(vf-vi)

Without time, it is impossible to generate force and

change velocity

Momentum

Ft = (mvf-mvi)

If masses are different, deficiencies can be compensated

for by increasing speed


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Implications for sport movement

Club/racket

Follow through Athlete body weight


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Ground reaction force

Implications for sport

movement Artificial turf

For every action there is an equal and

opposite reaction


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APA YANG TERJADI DENGAN TANGGA

TERSEBUT ???


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According to Rene

Descartes, the

human body is amechanical

system designed

by the hands ofGod.

HUMAN LEVER
http://images.search.yahoo.com/search/images/view?back=http://images.search.yahoo.com/search/images?p=rene+descartes&fr=yfp-t-331&toggle=1&cop=mss&ei=UTF-8&fp_ip=PH&vc=&w=256&h=273&imgurl=www.gla.ac.uk/departments/philosophy/Personnel/susan/Webpages0506/JadeBrian/descartes.jpg&rurl=http://www.gla.ac.uk/departments/philosophy/Personnel/susan/Webpages0506/JadeBrian/CartesianandPlatonicThought.html&size=4.9kB&name=descartes.jpg&p=rene+descartes&type=jpeg&no=1&tt=7,455&oid=647b7c2261f7b6b4&ei=UTF-8


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Borelli, a student

of Galileo,

considered thehuman body as a

system of levers.
http://images.search.yahoo.com/search/images/view?back=http://images.search.yahoo.com/search/images?p=human+body&ei=UTF-8&fr=yfp-t-331&fp_ip=PH&x=wrt&js=1&ni=20&w=612&h=445&imgurl=www.graphicwitness.com/medical/pix/body123.jpg&rurl=http://www.graphicwitness.com/medical/body123.html&size=44.7kB&name=body123.jpg&p=human+body&type=jpeg&no=9&tt=140,652&oid=7adecce17aa65f7a&ei=UTF-8http://images.search.yahoo.com/search/images/view?back=http://images.search.yahoo.com/search/images?p=borelli&ei=UTF-8&fp_ip=PH&js=1&ni=20&fr=yfp-t-331&b=41&w=150&h=221&imgurl=www.thebestlinks.com/images/thumb/1/18/150px-Giovanni_Alfonso_Borelli.jpg&rurl=http://www.thebestlinks.com/Giovanni_Alfonso_Borelli.html&size=7.9kB&name=150px-Giovanni_Alfonso_Borelli.jpg&p=borelli&type=jpeg&no=45&tt=13,198&oid=f08c430c4f6c558e&ei=UTF-8


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In our body, the bones act as the

rigid bar and the joints the

fulcrum.

It is through these so-called human

levers that we are able

to move, no matter how slight our

movement is,

to talk, walk, and eat.


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How it works: A rigid bar moves on fixed point when

a force is applied to it, to move object

Lever = rigid bar = bone

Fulcrum = fixed point = joint

Effort = force applied = muscle contraction

Load = object being moved = bone


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Levers are rigid bars (in the body, bones) thatmove around an axis of rotation (a joint) orfulcrum

Forces (supplied by muscles) cause the

movement to occur


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Magnify a force

A simple crow bar

Increase speed and range-of-motion

(ROM) Small amount of muscular contraction

proximally can produce lots of movement

distally

Balance torques A triple beam scale

Change direction of force

A seesaw or a pulley of a weight machine


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First, second, and third class

Arrangement of the applied force (effort),

the fulcrum, and the resistance determines

the classification Classification determines the levers

strengths and weaknesses


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Fulcrum in middle ( L F E ) (eg) scissors, moving head up and down

About 25% of the muscles in your body operate as first

class levers


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Axis

Force

Resist.

Example: Neck

extension


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Load in middle ( F L E )

(eg) wheelbarrel, standing on tip toes (not common inbody)

Very few occurrences in the body

Gain resultant force (you can lift more), lose distance


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Force

Resist.Axis


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Force in middle ( L E F )

(eg) using a tweezers, lifting w/ biceps 85% of the muscles in the body function

Usually produce speed at the expense of force

Greater lever length = greater speed (ex.)


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When the load is close to

the fulcrum, effort is

applied far from fulcrum

Small effort over largedistance = move large

load over short distance

(eg) Using a jack on a car


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When the load is farther

from the fulcrum than the

effort, the effort applied

must be greater than the

load being moved

(eg) using a shovel


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Perbandingan antara gaya otot dan gaya berat

Gaya berat (W) Gaya otot (M)

Iw IM

Keuntungan Mekanik =

w

M

I

I

M

W


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SAMPLE PROBLEM

A 120 N child and a 200 N child sit at the

opposite ends of 4.00 m uniform seesawpivoted at its center. Where should a 140 N

child sit to balance the seesaw?

2.0 m

120 N 140 N

R

W 200 N

FREE BODY DIAGRAM OF THE SEESAW


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(120 N)(2.00 m) + (140)(x) = (200 N)(2.00 m)

Solving for x, x = 1.14 m from the center

on the side of the 120 N child.


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Traksi leher

w

Arah tarikkatrol

Arah tarikotot


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w

Berat pemberat 1/7 kali BB


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Equilibrium is the state of zero

acceleration (static or dynamic)

Balance is the ability to control

equilibrium

Stability is a resistance to the

disturbance of equilibrium


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Low COG =

stability

High COG =

stability

1. Location of the center of gravity in relation to the base of

support2. Size of the base of support

3. Mass of the person

4. Height of the center of gravity

5. Traction/friction6. Sensory perceptions


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Center of Gravity (COG)

Titik di tubuh dimana seluruh berat dari

tubuh mempengaruhi

- Di tentukan bila akan menggambarkan tubuh sebagai

1 titik

- Secara anatomi tidak nyata dan mungkin terletak di

luar posisi tubuh

- Dipakai untuk menentukan pusat beban pada

gerakan- Dapat mempengaruhi stabilitas (seleksi petinju)


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DETERMINING THE CENTRE OF GRAVITY


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DETERMINING THE CENTRE OF GRAVITY

To determine ones COG, simply draw a box around the

objects outer extremities

Then draw diagonal lines through the box, with the point of

intersection determining the objects approximate COG.

www.flickr.com/photos/dearlydeparted/3834132754/ 46

Approximate

COG

STABILITY VARIES WITH BODY POSITION


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Low COG Higher COG

Wide base of support 4 point contact Small base of support 2 point contact

Line of gravity in middle of support Similar line of gravity

STABILITY VARIES WITH BODY POSITION

More stable Less stable

47PE STUDIES REVISION SEMINARS


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Bila benda mendapatkan gaya, maka benda

tersebut akan cenderung untuk berdeformasi

Tingkat deformasi tergantung besar gaya dan

tingkat kekakuan benda (karet dengan batu) Benda akan selalu beradaptasi dengan

gaya/beban yang menimpa. Bila adaptasi

gagal, maka benda tersebut akan rusak

Cth: cedera terjadi karena tubuh gagalberadaptasi thdp gaya luar.


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GAYA KOMPRESI

Lebih dari 1 gaya yang mendorong

benda pada arah garis yang sama

Cth. Gaya dorong/ tekan

GAYA TENSION

Lebih dari 1 gaya yang menarik

benda pada arah garis yang sama

Cth. Stretching

GAYA SHEAR2 gaya paralel yang mengenai

benda pada arah yang tidak 1

garis

GAYA YANG MENGENAI MATERIAL

STRESS


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STRESS

Deformasi materi/benda krn gaya kompresi

STRAIN

Deformasi benda karena gaya tension


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Stress = Load per cross

sectional area .

-resulting forcedistribution as a result

of an external force

Strain =deformation with

respect to the

original length

Normal Strain

change in length

Shear Strain

change in angle

Angle

Length Inlength


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Tabrakan pada mobil berkecepatan tinggi

menyebabkan penumpang mengalami gaya

percepatan atau perlambatan yang sangat

besar

Gaya-gaya ini dapat menyebabkan patah

tulang, cedera organ dalam dan kematian

bagi pengemudi maupun penumpang

Gaya-gaya yang bekerja tersebut dapatdiserap oleh kendaraan (bemper dan bagian

tubuh lainnya)


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Apabila percepatannya cukup besar tubuh akankehilangan kendali karena tidak memiliki gayaotot yang memadai untuk bekerja melawan gayapercepatan yang besar

Pada kondisi tertentu darah mungkin terkumpuldi berbagai bagian tubuh

Apabila seseorang mengalami percepatan dengankepala lebih dulu, kurangnya aliran darah keotak akan menyebabkan pandangan gelap dan

hilang kesadaran Jaringan dapat mengalami distorsi akibat

percepatan dan apabila gaya yang terjadi cukupbesar dapat terjadi robekan atau ruptur


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Sebuah benda mendapat gaya sebesar 30 N,

sehingga dalam waktu 6 detik kecepatannya

menjadi 30 m/s dari keadaan diam. Berapa

berat benda jika g = 10 m/s2?

Pada sebuah benda yang bergerak, bekerja gayasehingga mengurangi kecepatan gerak benda

tersebut dari 10 m/s menjadi 6 m/s dalam waktu

2 detik. Bila massa benda 5 kg, besar gaya

tersebut adalah ....a. 5N d. 10N

b. 6 N e. 11N

c. 8N


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F


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Pada 1905 Einstein :

teori baru

Kecepatan cahaya :

300.000 km/detik ;

kecepatan tertinggi di alam


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Al-Qur'an surat As Sajadah ayat 5 ,

kecepatan malaikat turun dari langit ke bumi &kembali menghadap Allah dlm 1 hari yang lamanya

= 1000 th menurut ukuran manusia

Dr. Mansour Hasaf ElNabi , ahli astrofisika MesirPerhitungan kecepatan cahaya :

[Jarak yang ditempuh oleh Sang Uruan ( Malaikat /nur ) dalam

satu hari ] = [Jarak yang ditempuh oleh bulan selama 1000 tahun

atau 12000 bulan ]

c = kecepatan cahaya

t = waktu selama 1 hari

L = panjang rute edar bulan

selama 1 bulan

c.t = 12000 . L


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Bila dihitung lebih lanjut

c . t = 12000 . L L = v . T

c . t = 12000 . v . T v = v* . cos c . t = 12000 . ( v* . cos ). T

v* = kec. Relatif bulan

T = periode revolusi bulan

t = 1 hari = 23 jam 56 4,0906 = sudut revolusi bulan

sehingga

c = 12000 . ( v* . cos ) . T / t

= 12000 ( 3682,07 .cos 26,928480 ) 655,71986 / 86164,0906

= 299792,5 km/detik

C perhitungan Al Quran C Einstein


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