Chapter 10 Bio-Mechanics and Sports for Grade XII students of Physical Education of CBSE board. All new topics covered

1. CHAPTER 10

2. CHAPTER 10

3. 10.1 Projectile and Factors Affecting
Projectile Trajectory
10.2 Angular and Linear Movements
10.3 Introduction to Work, Power and
Energy
10.4 Friction
10.5 Mechanical Analysis of Walking
and Running
BIOMECHANICS AND SPORTS

4. 10.1 Projectile and Factors Affecting
Projectile Trajectory

5. Biomechanics is the study of body
movements and muscular activities
Sport biomechanics is the study of
forces and stresses of human
movements & their effects on athletics
performance and safety.
It plays a crucial role in injury
prevention & performance enhancement
Biomechanical analysis benefits
athletes of all ages and skill levels.
BIOMECHANICS & SPORTS

6. Object thrown into air horizontally or at an acute
angle under the action of gravity is called projectile
There are 2 forces acting on it gravitational force and
air resistance
The path followed by a projectile is called its
trajectory and it is a parabolic path.
PROJECTILE

7.  Initial velocity
 Angle of projection
 Projection height relevant to the landing surface
 Air resistance
 Surface area of the projectile
 Surface to volume ratio
 Mass
 Velocity
 Gravity
 Spin
FACTORS AFFECTING PROJECTILE TRAJECTORY

8. Initial velocity is directly related to the distance covered in
flight. The speed of release depends on initial vertical velocity
and initial horizontal velocity. Having higher horizontal velocity
will increase the distance covered.
INITIAL VELOCITY AFFECTING PROJECTILE
TRAJECTORY
Angle of projection same and initial velocity changing

9. An object which is projected at different angles but the same
initial velocity covers different distances. When it is released
at an angle of 45, covers maximum distance.
ANGLE OF PROJECTION AFFECTING PROJECTILE
TRAJECTORY
Angle of projection changing and initial velocity same

10. The higher the level of release, the longer distance is covered
in flight. The horizontal component will be acting on the
projectile for longer duration, hence projectile will be covering
a longer distance.
HEIGHT OF RELEASE AFFECTING PROJECTILE
TRAJECTORY

11. Gravitational force is exerted by earth on all
the objects.
Gravitational force is constant for all the
objects
Gravitational force decreases at the places of
high altitude
Performance in jumps and throws is better at
the places of high altitude
GRAVITY AFFECTING PROJECTILE TRAJECTORY

12. Amount & direction of spin directly affects the
distance covered
If the spin creates low pressure on the top, the
object remains in air for longer period covering
longer distance
If the spin creates high pressure on the top, the
object remains in air for shorter period and
covers shorter distance
SPIN AFFECTING PROJECTILE TRAJECTORY

13. When a projectile moves through the air, it is
slowed down by air resistance.
Air resistance decreases the horizontal
velocity of the projectile
AIR RESISTANCE AFFECTING PROJECTILE
TRAJECTORY

14. 10.2 Angular and Linear Movements

15. Change of position of a body. Consists of
upsetting the equilibrium of a body.
Linear Motion
 When a body moves in a straight line, from
one point to other in the same direction
 The direction can either be in a horizontal,
vertical or inclined direction.
 Measured in feet, meters, KM etc
MOTION

16. Motion of a body about a fixed point
All points on a body move in a circle about the
same fixed central line or axis
It can occur about an axis within the body or
outside the body.
Measured in degrees
ANGULAR MOTION

17. Axis Outside the body (Visible Axis)
Axis Inside the body (Invisible Axis)
ANGULAR MOTION

18. 10.3 Introduction to Work, Power and
Energy

19.  An activity involving a force and the
movement in the direction of the force.
It is defined as the product of constant force
and the distance moved in the direction of
the force.
Work Done = Constant force × Distance
moved in the direction of the Force
(displacement)
W=F X S . Unit is Joule
 If barbells weigh 1000 N &
weightlifter lifts it to 1.5 m
work done = 1000 X 1.5
1500 joule
WORK

20. The rate of doing work or rate of using
energy is called Power.
work done
Power =
time taken to do work
P = W / T Where P = power in watts(w)
W = work done in joule (j)
T = time taken in seconds (s)
POWER

21. The Energy is the capacity to do work.
There are various forms of energy but in
the field of sports , main concern is about
mechanical energy
Mechanical energy is the combination of
kinetic and potential energy.
ENERGY

22. Kinetic Energy(KE) : Energy possessed
by a body as a result of motion.
KE = ½ * mass * (velocity)² joule
 KE = ½mv² joule
Potential Energy(PE) : Energy which is
stored in a body because of its position
PE = mass × gravitational force × height
of the body from ground joule
PE = mgh joule
 Energy can be transformed from kinetic
to potential and vice versa.
ENERGY

23. ENERGY TRANSFORMATION IN POLE VAULT JUMP
End of run-
up
Take-off
Time (s)
Energy
Max
Pole bend
Pole
Release
t=0
t=1.6 s
peak
KE min
PE min

24. 10.4 Friction

25. Opposing force between the two surfaces that
come in contact.
Always acts in the opposite direction of the
applied force
Allows us to walk, run, play sport
Lubricants reduce friction
Types of Friction
1. Static Friction
2. Dynamic Friction
a) Sliding friction
b) Rolling Friction
FRICTION

26.  Opposite force that comes into play when one
body tends to move over the surface of another,
but the actual motion has not yet started
 Static friction is the friction that exists between
a stationary object and the surface on which it's
resting
 Once the object starts moving, Dynamic (kinetic)
friction takes over
STATIC FRICTION

27.  The opposing force that comes into play when
one body is moving over the surface of another
body. Dynamic friction may
 Types of Dynamic Friction
1. Rolling friction: Opposing force that comes
into play when one body is rolling over the
surface of another body. For example, wheel,
rolling skates,
2. Sliding friction: Opposing force that comes
into play when one body is sliding over the
surface of another body. For example- Ice
skating.
 Rolling friction is less than sliding friction.
DYNAMIC FRICTION

28. EXAMPLES OF DYNAMIC FRICTION

29. Advantages of Friction Disadvantages of Friction
Due to friction, the objects can be
placed at position and shaped.
Due to friction, there is wear and tear of
objects. Lubrication is used to allow the
parts to move easier & to prevent wear
and tear. Greasing is done in the moving
parts of Bicycle.
Frictional forces help to move the object
by friction. It helps in running, walking.
Frictional force helps to move the object
with high speed. For example:- Spikes
are used by the athletes to run fast.
Studs in soccer.
Friction makes it more difficult when
one has to move the object. Excess
friction can make it difficult to slide a
box across the floor, walk through deep
snow.
With the help of friction, the ridges of
skin of our fingers and our palm enable
us to grab and hold objects. For
example- In badminton the players use
grip to hold it.
In the roller Skating, Rolling Shoes and
smooth surface are used to minimize
friction. Wooden floor used for cycling
The energy lost due to friction in trying
to move the object is turned into heat
energy.
Excess of friction means extra energy,
thus energy is being wasted.

30. 10.5 Mechanical Analysis of Walking
and Running

31. Running Walking
Running is a process, in
which both feet are off the
ground. (float phase)
Walking is a process, in which
at least one part of body (foot)
remains in contact with the
ground.
There is a double swing phase
and the swing phase is longer.
There is longer stance phase
where as swing phase is
shorter.
The linear and angular
velocity of lower limbs is
faster
The linear and angular
velocity of lower limbs is
slower
Running requires greater
range of motion
Walking requires lesser range
of motion
DIFFERENCE BETWEEN WALKING AND RUNNING

32.  Stance phase:- Stance phase is the time, when
the foot is on the ground. It consists of
maximum percentage of walking cycle. For the
part of stance phase, both the feet have a
contact with the ground
 The stance phase of walking is divided into five
stages.
1. Heel Strike
2. Early Flat Foot
3. Late Flat Foot.
4. Heel Rise
5. Toe off
MECHANICAL ANALYSIS OF WALKING

33. Heel Strike - foot first touches the ground and
continues until the complete foot is on the
ground
Early Flat Foot - complete foot is on the ground
and early flat foot stage occurs when body’s
centre of gravity (CG) passes over the top of the
foot. Purpose of this stage is to allow the foot to
act as a shock absorber.
Late Flat Foot - body’s CG passes in front of ‘
neutral position. Stage lasts when heel lifts off
the ground. Foot moves from being a shock
absorber to being a rigid lever helping to propel
the body in forward direction.
STAGES OF STANCE PHASE OF WALKING

34. Heel Rise - Heel begins to leave the ground. The
foot functions as a rigid lever to move the body
in forward direction.
Toe off- Toes leave the ground completely. This
stage continues until the beginning of swing
phase.
STAGES OF STANCE PHASE OF WALKING

35. It occurs when one foot is on the ground and other
one is in the air.
Swing phase in walking is shorter than the stance
phase.
Divided into 3 stages
1. Initial swings:- Hip is extended to 10º and then
going onto flexion and knee flexed to 40-60º and
the Ankle changing it’s position from the flexion to
neutral.
2. Mid swing:- Hip is extended to 30º, the knee flexion
till 60º and extended approx to 30º and ankle
become dorsiflexed.
3. Terminal Swing:-Hip is flexed till 30º and the knee
is locked extension and foot changes its position
from Dorsiflexed to neutral
STAGES OF SWING PHASE OF WALKING

36. 
MECHANICAL ANALYSIS OF WALKING
Main Joints
that move
during walking

37.  Stance phase:- Stance phase is the time, when
the foot is on the ground. During this phase, the
foot and leg bear the body weight.
The stance phase of running is divided into four
stages.
1. Initial contact stage
2. Braking or absorption stage
3. Mid-stance stage
4. Propulsive stage
MECHANICAL ANALYSIS OF RUNNING

38. 1. Initial contact
After completion of float phase , the moment one foot
touches the ground is called initial contact and marks the
beginning of the stance phase. The other foot behind you
is off the floor and in swing phase.
2. Braking (absorption)
The moment one foot makes contact with the ground in
front of you, body is now performing a controlled landing,
managed via deceleration and braking. Front knee and
ankle flex and the foot rolls in to absorb impact forces.
During this process of absorption, the tendons and
connective tissue within the muscles store elastic energy
for use later in the propulsion phase.
STANCE PHASE OF RUNNING

39. 3. Mid-stance
The braking phase continues until the front leg is directly
under the hips taking maximum load as the body weight
passes over it. The ankle and knee are at maximum flexion
angle. This moment is called mid-stance
4. Propulsion
Body weight has gone forward of the front foot . Now, this
foot starts to propel you forward. This is achieved by ankle,
knee and hip all straightening to push the body up and
forwards, using the elastic energy stored in braking phase.
The propulsion phase ends when the toe of front foot (now
behind you) leaves the ground, commonly referred to as
“toe off” (TO) & you are once again in float phase.
STANCE PHASE OF RUNNING

40. At the moment of toe off, one leg has travelled as far back
as possible and the heel starts to lift. The height the heel
reaches and the returning drive of the knee is dependent on
the power of hip extension achieved, and will be greater at
higher speeds.
stretch reflex mechanism is compared with stretching back
of a sling shot and then letting go. Extension of hip is
equivalent to pulling back on the sling shot.
Letting go results in the leg firing forwards rapidly, leading
with the knee. Once the knee has passed under the hips, the
lower leg unfolds in preparation once again for initial
contact, marking the end of the swing phase.
SWING PHASE OF RUNNING

41. MECHANICAL ANALYSIS OF RUNNING