2. Bio –life,
Mechanics– machine in force
MECHANICS
-science deals with forces and the effects of forces,specifically the motion and
deformation of solid,liquid and gaseous matter.
KINESIOLOGY-
-STUDY OF MOTION ,developed from the faacination of human beings like
‘how does a person walk’,’what are the limits of muscular strenght”
From the quest for answers these questions
Science of motion evolved,combining theories and principles from
anatomy,physiology,psycology,anthropology and mechanics.
THE APPLICATION OF MECHANICS TO THE LIVING HUMAN BODY IS
CALLED BIOMECHANICS.
OR
BM IS A BRANCE OF SC.THAT DEALS WITH FORCES & THE EFFECTS OF
FORCES ON LIVING SYSTEM AND MATTER.
3. Clinical Kinesiology;-
-study of force acting on the human body and to use their force in
treatment etc.to improve performance and prevention from any kind of
injury,.
MECHANICS
STATICS DYNAMICS
-concerned with bodies at rest -which treats bodies that
Or in uniform motion. Are accelerating or dece
-lerating
DYNAMICS:-
1)Kinematics
2)kinetics
4. KINEMATICS:-
-force + movement
-science of the motion of bodies in space and it applies co-ordinated system to
explain the movement of a single point of the body,position of the several
segment of movement between adjacent joint surfaces.
Sub-division:-
1) Osteo-kinematics=deals with the movt. Of bones or any bony segment
(ROM).
2) Arthro-kinematics=deals with the movt. Between the jt. Surface,includes
gliding,sliding,rolling,spinning etc.
KINETICS
-force only either internal or external forces.
5. CENTER OF GRAVITY(COG) AND LINE OF GRAVITY(LOG)
GRAVITY
-is the force by which all the bodies or masses are attracted towards the earth.
-the force of G acts continously upon the human body,and if unopposed the latter
will fall to the ground.
-the effect of G can be counterbalanced when a force equal and opposite to it is
employed.
-if,however,G is opposed by a force which is greater,movt. Will occur in the
direction of that force.
COG
-is a position or a point in the body at which the sum of all the forces is equal to
zero and at this point the body can remain motionless.(any position).
6. FACTS ABOUT THE COG IN HUMAN BODY
-it is located in the vicinity of the vertebrae i.e.mostly S2.
-it is higher in position in male than in female.
-in male,COG lies at 56.18%-58.18% of their body height.
-in female,COG lies at 55.44% of the body height.
-the variation of position of COG will be anywhere between 55-59% of body ht.
at diff. ages.
-by the age of 60-70 yrs,the COG decreases gradually from T7 to S2.
-however the location of the COG varies with build,age and sex also to the
position,ex-in standing COG is at its highest pt. & in supine lying COG is at
minimal ht.
7. LINE OF COG
-is an imaginary line drawn through the COG of the body.
-In standing,the LOG passes through mid pt. btwn 2 legs then through S2 then
passes through lumbar region then in front of thoracic vertedra & finally through
mid cervical vertebra anteriorly.
8. DISPLACEMENT OF COG WHILE WALKING
1) VERTICAL DISPLACEMENT.
-in normal walking pattern the COG goes through a rhythmic upward and
downward motion.
-highest pt. occur at single leg stance due to reduce BOS & the lowest pt. occur
during double support time as the BOS is maximum.
-VD is about 5cm or 2 inches totally.
2) LATERAL OR HORIZONTAL DISPLACEMENT
-COG shift from left to right position & vice versa as the wt. is transferred from
one leg to another as the pelvic & trunk shifts towards the wt. bearing side.
-it is 5cm or 2 inches.
9. BASE-
-it is the area by which the body is supported either on the ground or any other
mode.
-braoder the base better is the stability as COG shifts towards the broader base.
BALANCE
-is the state in which the body is in equillibrium & the resultant of forces acting on
it is zero.
-it depends upon the BOS & position of COG & LOG.
-In human beings the control of balance depends upon integrated action of sensory
motor system.
TYPES OF BALANCE
1) STATIC BALANCE
2) DYNAMIC BALANCE
10. STATIC BALANCE
-it is a rigid stability of one part of a body and is based upon co-contraction of the
muscles.
DYNAMIC BALANCE
-unless the body is fully supported & relaxed it is in constant state of change and
adjustment to maintain its posture and equilibrium.
-here isotonic contraction of muscles take place.
CONTROL OF BALANCE
1) CNS:-
-level of muscular contraction.
-velocity ------------------------
-timing----------------------
2)PERIPHERAL NS(PNS)
-regulates proper neural response
-jt.segment response
-muscular response
11. 3) OTHERS
-visual ctrl
-vestibular ctlr
-proprioception ctrl (pressure and tension of jt.)
-tactile ctrl
-psychological factor
-environmental factor
12. FACTORS PLAYING ROLE IN STABILITY OF HUMAN BODY
1) The relation of LOG & BOS.
2) The size & shape of the BOS.
3) Ht.of the COG.
4) Mass of the body.
PRINCIPLES OF STABILITY
1) The lower the COG the greater will be the body stability
Application: performer in a balnace beam squats down in order to
maintain the balance.
2) Wider the BOS greater is the stability
Application: pushing or pulling a heavy furniture.
3) For max.stability the COG should enters the BOS at a pt. which allows the
greater range of motion within the area of base.
13. EQUILIBRIUM
-State of balance b/w opposing forces.
CAN BE STUDIED UNDER FOLLOWING CONDITIONS.
1)≈ under static condition
2)---------dynamic cond.
3)----------in water
UNDER STATIC COND.
-STABLE
-UNSTABLE
-NEUTRAL
14. STABLE EQUILIBRIUM
-where the potential energy is at its minimum & work must be done on.
Eg-body lying down on a horizontal surface.
UNSTABLE
-WHER P.E is at its max.and BOS is extremely small.
NEUTRAL
-here P.E remains constant with very little or no change in the ht. of COG
15. EQUILIBRIUM UNDER DYNAMIC COND.
1) Equilibruim over a minimal base
-single leg standing
2) eq. over a changing base
- gymnasts
EQ.IN WATER
Buoyancy & center of buoyancy:--
-buoyancy is the upward thrust that any fluid exert on an object or body which
partially or entirely immersed in the fluid and the force of buoyancy is always
equal to the wt. of volume of the fluid that has displaced by the object.
ARCHIMEDES PRINCIPLE
CENTER OF BUOYANCY
-COB is located in the area which displaces the largest volume of water.
- In human,COB lies in the thoracic region for a fatty person and normal lies at
region oh hip or thigh.
16. STATIC EQ. IN WATER
-occurs when COB & COG lies in same vertical line.
eg—for the swimmer who tries to float motionless,his body will rotate untill
COB or COG comes in a vertical line.If an individual floats at a large angle with a
horizontal he will maintain the eq.easily.
DYNAMIC EQ. IN WATER
-maintain in the water as long as the swimmer keep the orientation of own body
horizontal or near horizontal.
17. FORCE
DEFN.---it is an action which brings about a change in the position of the body.
--it is pull or push from one place to another.
---it is better quantity responsible for the change in the state or motion of
of the body.
CHARACTERISTICS OF FORCE
--magnitude
--direction
--line of action
--point of apllication
18. MAGNITUDE (quantity)
--magnitude of muscular force is directly propotional to the size of fibre which
are contracting.
DIRECTION
-the direction of muscular force is determined by relation of tendon to
mechanical axis of the bone.(the straight line connecting the mid point of joint)
--the angle b/w M.axis of the bone & muscle line of pull=ANGLE OF PULL.
it change with every degree of motion.
LINE OF ACTION
-is the muscle line of pull in which direction of pull is indicated by an arrow
mark.
POINT OF APPLICATION
--this is the pt. at muscle where force act on a segment.
19. COMPONENTS OF MUSCULAR FORCE
For producing a movt. Or motion,the muscle must pull a segment at an angle
to the bone MA except when the mus. Is pulling at exact 90 degree.
It produces 2 components:-
--rotatory comp.
--non rotatory or translatory comp.
ROTATORY COMP.---responsible for bringing of movt.
---always perpendicular to MA
NON-ROTATORY -----stabilisation
----parallel to the axis
***when the angle of pull is 90,the force is completely rotatory.and when it is
45,both the components are equal.
20. NEWTON’S LAW
1ST LAW
----every object remain in a state of rest or uniform motion in a straight line untill
act upon by the external force.
2nd LAW
----if body having mass (m) having an acceleration(a) then the force acting on it
will be product of
f=m*a
3rd LAW
-----for every action there will be equal and opposite reaction.
21. FORCE SYSTEMS
1) COLLINEAR F.S.
--they are the force acting in at single line.
--negative force(arrow directing toward left or anti clockwise)
--positive force(arrow towards right and clockwise)
resultant =summation of all the forces acting either +ve or –ve.
2) CO-PLANAR F.S
--also known as parallel force system.
--here forces are apllied at some distance far from each other.
3) CONCURRENT F.S
--also known as co-incident force system.
--here action line of each force meet at a point which being applied to a body
from two or more different angles.
types:convergent & divergent
eg .in human-- deltoid
22. FORCE COUPLE
--is a parallel force occurs when two forces of equal magnitude acting at an
equal distance from each other and opposite in direction.Since the two forces
are equidistant,it will produce a turning action without linear displacement/.
FORCES MODIFYING THE MOTION
1) Rebounding force
2) Fluid force
3) Frictional force.
23. REBOUNDING FORCE
---here object after colliding repels backward or propagade forward with gaining
some ht.
the nature of the rebound is determined by
:elasticity
:mass
:velocity of rebounding surface
:angle of contact
:friction b/w 2 surface
ELASTICITY
----ability of the object to resist destorting influence and to return to its original
shape and size when the destorting force is removed.
The force which act on an object to distort is known as STRESS.
The distortion which occurs =STRAIN
24. MASS
---lesser the mass greater will be the rebound and vice versa.
VELOCITY
---F=ma
FLUID FORCES
--medium dependant
FRICTION
The friction occurs when one body slides in relation to another.
The friction force or the shear force occuring b/w an adjacent surfaces follows
Newton’s 3rd law
25. CHARACTERISTICS OF FRICTION
-is the force which opposes the effect to slide or roll of one body to about another.
-without friction it is difficult to perform activities.
-the amount of friction b/w one surface & another depend upon the nature of
surface & the force pressing them together.
-force of friction act parallel to each surfaces.
TYPES OF FRICTION
1)STATIC FRICTIOB
2)SLIDING
3)ROLLING
26. STATIC FRICTION
--type of friction which resist start of motion.
LAWS—
1)Friction force b/w two surface in contact oppose their relative motion.
2)As long as two bodies are in contact & are in eq. the frictional force just present
the relative motion b/w them.
3)The frictional force is independent on area of the contact of the body ,it depends
upon the nature of the surface in contact & condition of the surface.
SLIDING FRICTION
-friction that resist the continued motion.
--it occurs at the transition from static to dynamic condition.
LAWS—
1) THE frictional force acting to the parallel surface in contact is always opposite to
the direction of motion.
27. 2) It is independent on the area of contact & dependent on speed of sliding.
3) When the force applied to the body in contact to another body is just enough to
overcome the friction force of the body.Then the body begins to slide over the
otherwith the uniform velocity.
ROLLING FRICTION
--friction during rolling movt.
--inorder for rolling friction to occur deformation of either the body or surface
must takes place.
28. POWE R
---rate at which the work is done.
---the work capacity of any muscle is related to amount of force or tension.
power=work done/time taken
=Force * distance/t
Steps for finding mechanical work performed by individual muscles.
-find the cross section area of the muscle.
cross section=width * thickness
-find the amount of force exerted by muscle .
F=average force* cross section
29. TORQUE
-- is equal to product of force magnitude and its perpendicular distance from
the direction of force to the axis of rotation.
This perpendicular distance is known as MOMENT ARM.
The turning effect of force is known as torque.
t=fm*d fm=force of movt.
d=perpendicular distance
It is seen ion force couple.
The muscle forces also exerts the torque on a rotating segment & it depends
upon both magnitude of muscular force and length of moment arm.eg. Elbow
jt.
30. PRESSURE
--total force applied per unit area.
p=f/a
SPEED
--rate at which the body move and take no account of direction
VELOCITY
--rate at which the body move in a definite direction.
STRESS
--when a deforming force is applied to a body,internal forces are generated in a
body which oppposes the deformation and tend to restoree body wt.in original
cond.
So stress can also be described as restoring force inside the body per unit area.
s=f/a
31. TYPES OF STRESS
1) Compressive stress(is –ve)
2) Tensile stress(is +ve)
STRAIN
-----the ratio of change in any dimensions of the body from the original dimension.
Strain=change in dimension/original dimension.
It is a relative major express as % & thus has no unit.
TYPES OF STRAIN
1) Linear strain-change in the length of the body
2) Volume strain
32. HOOKE’S LAW
-----strain is directly proportional to the applied stress.
STRESS STRAIN CURVE.
1)Elastic phase----is the phase when a material is stretch within its elastic
limits,the strain or deformation is reversible.this is the region in which it is safe to
stress
2) Yield point----occurs when the material stretches for a period without
additional forces.
3) Plastic phase---permanent deformation of the material occur when the stress is
applied.In this phase hooke’s law is no more applied.
4) failure------occurs after the plastic phase and in this phase the material deform
and looses its properties.
