Unit

Biomechanics
and Sports

e,IJ.S.E, Syllabus

After studying this chapter, students will be able to understand :

0 Newton's
Law of Motion and its application in sports
0 Types of levers and their application in sports
0 Equilibrium - dynamic and Static and centre of gravity
and its application in sports
0 Friction and sports
0 Projectile in sports

I INTRODUCTION

Now-a-days every player wants to improve his/her performance to achieve success and fame. Trainers and coaches
help their trainees by using or applying principles of biomechanics in their training sessions. Understanding the
importance of biomechanics in sports many institutions are laying special stress on imparting fundamental motor
skills among their students to improve their sports performance.
Meaning of Biomechanics
It was realised afte~that the mechanical principles involving on the
human body is entirely different from other things. So, during the early
1970s the international community adopted the term biomechanics to
describe the application of mechanical principles in the study of living
organisms. The term 'biomechanics' is a combination of two words i.e.,
' ~ d 'mechanics'. Here, 'bio' refers to life or living things and
'mechanics' refers to those forces which act on a body when it is in motion.
Therefore,
Biomechanics is study of human body as a machine. Various internal and external factors that affects
the speed and movement of body are studied under this subject.
Bi~mechanics is a sub-discipline of physical education in which human movements are studied by applying
Pnnciples of mechanical sciences. In other words, ~iomechanics is s~~ of effects of forces on living bodies. This
study of movements of body, also observes those internal and external forces which apply on a body and those
movements which these forces -

Physical Education-Xll (Biomechanics and Spons) 205

 • .. ws or Motion
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~ffnlllon or Blomechanla 1--------------------- of 1ne
rtia (First Law) : Newton's Law of inertia slates that- the
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resist changes in their
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o "BiomL-chanla i1 concerned with the Internal and external forces acting on a human body and the
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orion and rest. no ect m motion Wtll tend to stay in motion and an object at rest, will tend to s ...y
acted u~n by a force.~
effochi produ<'l'd by thew forces". -Jt,mt• G.H~ ,t ~ don in Sports
o '11,e area of ,tudy where the knowledge and method• of mechanic:a aN! applied to the structure and M'l'uca tball placed at penalty point will remain at rest unless a player kicks the ball (force applied) to move
function of ti~ living human system", -Mn-"m Wtb,tnDicHont,ry o "":,u 1owa<ds goal•po,1.11 wHI move U, the dfr«tion when, the play,,- had e,,,te,i th~ fo,a, lh~gh
~;k Similarly, The body of a player quickly sprinting down the field will tend to retain that motion
ki • a force acts upon him.
Importance or Blomechanlcs In Sports unless
(a) Improve, Performance In Sport• : Principles of blomechanics tell us about right techniques, effective and
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result oriented posture to get more efficient results by applying minimum muscular force which in turn
lmprove1, pl•rformance In sports.
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(b) Improvement In Technique: With the help of biomechanical principles the physical education teacher corr
the mistakes. This helps In improving the game and performance of the player. ects
(c) Development of Improved Sport• Equipment: The principles of biomechanics a~e used to modify the Sports
equipments. For <.'xample, tee shirts, studs, spikes, swimming costumes, hockey sticks, different size footballs
and low weight helmets for protection.
(d) Improve In Training Techniques : A teacher can analyse the player's movement or action with the help of If you slide a hockey puck on field, eventually, it will stop because of friction on the field. It will also stop
the biom<.'dlanical principles. It helps in improving the training techniques. o if it meets something like a player's stick or a goal post. •
(e) Prevent• Sports Injuries: It helps to find out the factors or the forces that can lead to the injuries during the A skater gliding on ice will continue gliding with the same speed and in the same direction unless an
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game situation. It also helps in prevention of the sports injury. extemal force acts upon the skater.
(f) Help■ In Understanding Human Body: It gives the knowledge of different systems of our body. For example, Law of Motion (Second Law) : Newton's law of motion precisely explains how much motion a force creates.
nervous systc•m, muscular system and skeletal system. 2, Aecording to this law-The rate of change of movement is proportional to the resultant force and takes place
(g) Knowledge of Safety Principles : Biomechanics gives the understanding lo analyse different movements in the direction of the force applied. ~ • --
that can harm the player. TI1e teachers remove those unnecessary and harmful movements.
0 When a force acts on an object, the acceleration of the object it produces is directly proportional to the
(h) Help• In Research Work : Biomechanics helps in teaching and learning process. It also helps the teacher to magnitude of the force applied and that too in the same direction of the force and inversely proportional
acquire precision and accuracy of movement. to the mass of the object.
(I) Createa Confidence In Player: The player knows that he is executing the movement scientifically with the 0 The more mass the thing has, the more net force has to be used to move it. For example, if you use the
help of principal of biomechanics. Thus the confidence of the player is enhanced. same force to push a truck and push a car, the car will have more acceleration than the truck because the
(j) Help• In Maintaining Healthy Body: Principles of biomechanics give deep knowledge about the effect of car has less mass.
physical forces and movements over the body as well as the movements which are safe and promotes health. Application in Sports
Thus biomechanlcs helps in maintaining healthy body. o A volley ball player pushes the ball slowly for a drop whereas hits the ball hard for a smash. Thus drop is
(kl Increases The Popularity of Sport■ : Biomechanical principles have brought remarkable improvements in slow as there is Jess force whereas smash is very fast as there is greater force involved.
respect of technique, equipment, skill and play fields. It helps in promoting the games and sports in the o In a shot-put event, a player who exerts more force and tosses the shot-put at cwrect angle has greater
masSt.>S. displacement of shot-pu_t, whereas a player who exerts less force has lesser displacement of shot-put.
Ill NEWTON'S LAWS OF MOTION AND ITS APPLICATION IN SPORTS
Newton's Three Laws of Motion explain how forces create motion in our daily life. These laws are usually referred
to as the Law of Inertia, Acceleration, and Reaction.
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Sir luac Newton ( 1642-1 ?~was one ofthe greatesl scientists and mathema1icians that ever
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lived. Newton came up with tlil!egeneral rules about the movemenl of objects, which are ·. ·,' '\
now known u Newton'• three laws ofmotion. -,.;..;",.. "=\\.. .IA._ - - L .,
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 -> ~ ..,"'"'"' • r'--~-~ "·ill "'luirc mott force to kick the ball • er. Th·1 c;eeJeration due to an external force acting on a moving object is technically defined .u change in that object's-
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, ~wt of It~"'"'. (Thlnl. l.•wl'I I Amihrding to the Law or Re •
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L,oCation (b) Direction
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(a) . nol the importance ofbiomcchanics7
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rovement of technique
To understand the structure of movement and effect of forces on the movement
o A.,....,. I"'...,. th< w•"' t,.,d-w•nl• (,ctfon). The w,te, •
"·ith tht ull\l' klf\~. pushes the sw· (b) nderstand physiology of human body
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rovement of sport equipments
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gun or .(.... d) 3-(c), 4-(d), 5-(b), 6-(c), 7-(c), 8-(c)
J-(a), 2-( •
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- . ---, Jerks ~ fine biomechanics. (CBSE Ttxtbook)
,. :at do you understand by the concept ofsports biomechanics? Write in your own words. (CBSE Ttxtbook)
~ Aclion force ~
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JO. (.isl the importance of spons biomechanics. (CBSE Tt.ttbook)
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JI, Jj ,Newton'sLawsofMotion. (CBSE Ttxtbnok)
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~idateNewton'sLawoflnertia. (CBSE Textbook)
El th the help ofsuitable examples, discuss the application ofNewton•5 Laws of Motion in sports. (CBSE Ttxtbook)
Reaction force J4. !w can Newton's second law and third law of motion be applied in sports? (CBSE Ttx1book)
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Ac:tionfofet J4. Biomechanics helps to improve technique and equipment ofsports. Explain with suitable examples. (DoE)
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' ----<.., •••" - . _ _ _ : Wh I is biomechanics? How ii helps 10 promote sports and games. (DoE)
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When an athlete runs, he/she presses the .ground
• m .theh backward direction (action) by his/h
0 ground pushes him/her in the forward d1rection wit an equal force (reaction). er feet. 11ie • LEVERS AND ITS ~YPES
While jump, our legs apply force to the ground, and the ground applies e 1
0 · f ) th I · th • qua and oppos· er is a rigid bar/rod that 1s used to apply and modifies force which is applied at two points, and it
force (ground reaction orce at prope s us mto e air. 1te "action
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When a basketball player dribbles, he/she exerts force on the ball and the ball trik IUJ1IS the third pom •
0 force (action). Then, the ball comes up with an equal force from the floor (reac es on the floor•With a
s tion). isa simple machine that makes work easier for us, it involves moving a load or work around a pivot (fulcrum)
~ rorce, lt consists of a beam or rigid rod or bar pivoted at fixed point (fulcrum). Many of our basic tools such
USJll~.1.e11rs plier, nut cracker, pulley, tongs, sea-saw etc. work on lever mechanisim.
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All lever systems are made up of four components :
I. Thetenn 'biomechanics'todescribc the application of mechanical principles in the study oflivingorganisnnvas L Load: It is the object that requires movement.
adopted in: (CBSE TutboolJ 2, fulcrum : It is the point at which the lever rotates or turns and identifies the lever class by its positio~ in
(a) Early 1970s (b) Lale 1970s (c) 1970 (d) Early 1980s relation to the other two parts. In human movement, the fulcrum is the joint that dictates the kind of action.
l The field where the study offorces is in focus is known as (CBSE Textbook) 3. force/Effort Arm : It is the point at which the force is applied.
(i) Dynamics (b) Kinematics (c) Statics (d) Kinetics '- Lever: It is a bar used to overcome resistance when force is applied.
l Sports biomcchanics can be described as- (CBSE Tt.ttboot) (.eyftSmechanasim is also found in our body (skeletal system) due to which our actions, movements take place.
(i) Mcchanicsofsports (b) Kinesiology (c) Physicsofspons (d) Sponsdynamics For aamplt-
4. According lo Newton's Second Law of Motion, the greater the movement of an object, the : (CBSE Tt;book) o The 'load' is the joint around which the movement occurs.
(a) Longer distance will ii travel o Body joints (pivot) act as 'fulcrum'.
(b) SIIOllgcr will it resist the external forces o 'Effort' is done by contracting muscles by exerting force.
(c) Speedier it will cover the given distance o The bones of the skeleton acts as the 'lever'.
(d) Min stable will it remain in its motion. Standard symbols of lever system :
5. Newton's FIISI Law of Motion is !mown as the : (CBSE Ttxtbook) Lever systems have some standard symbols that represent it's part.
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(1) LawofRCllClion (b) Lawoflnenia (c) LawofEffect (d) LawofMomentum
6. Newton'sSccondLawofMotion is also known as:
__(a) Law of Reaction (b) Law oflnenia (c) Resultant Force (d) LawofEffect
(CBSE Ttxtbook)
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Load Fulcrum Effort Lever
_,~J, 208 (Biomechanics and Spons) Physical Education-XII [ 1· ]Physical Education-XI/ (Biomechanics and Spons) 209
 Types or Levers
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..,...plet: an individual stands on tiptoe; the length of the foot is the arm of lever, the ball of the foot acts
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There are thl"l.'1! types/classes of levers: FOrU- jO wi,en fulcrum and Achilles, tendon and calf muscle provide the effort (force), lifting the weight of the
,s the the back of the heel.
L ~u-lbver:
t,odY by • g V-sit-up, Fulcrum (Ball of the foot), Effort (Arm muscle contraction) and lo;id (Body weight),
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0 1,ever:
o,st'3 of levers have the effort (force) between the load (resistance) and the fulcrum.
0 'J11est• type
class of lever, the force arm is always shorter than the resistance arm due to which large amount
Fulcrum
r (joint in n«k) In force
O of thtS ,s • requ ired to do the work. In the human body ii is the most common class of lever.
Force ..~
d111ples:Of sports equ1•pments use class-3 levers, including baseball bats, tennis rackets, boat paddles, etc.
Load Foret (applied by 0 A fol
muscles) our tore-arms a (so act as class -3 lever with the elbow as the fulcrum.
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Fig. Class-I Lever
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EITort
load
O These type of levers have the fulcrum between the effort (force) and load (resistance).
O This class fulcrum can be moved to change the relative lengths of the force arm and the resistance ann.
O li the fulcrum is placed close to the resistance then less force is required to be applied through long
•Fulcrum
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distance to move the resistance a short distance.
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0 Similarly, a shortened force arm requires more force, but there is a gain in speed and range of motion at
the resistance end.
Examples: Fulcrum:
Elbow joint flexes } toad:
O When throwing a ball, Fulcrum (Elbow), Effort (Triceps) and Load (Ann/ball). as biceps contl'IC1 ~J~::""'--..
O While doing V-sit-ups, Fulcrum (Hip joint), Effort (Abdomen) and Load (Leg/Lower body).
2. Class-2 Lever : A fishing pole is also a class-3 lever where hand at the end of the pole is the fulcrum and the fish you
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catch on the opposite end is the load and the hand between the fulcrum and the fish (load) applies
effort (force).
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Other examples of class-3 levers are- seated bicep curl, leg extension, hamstring curl, etc.
Ful<rum:
J01nt1 at the ball of the f1

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Effort:
• Fulcrum
Calf muse.let conll'ICI and lift
body weight

t ,-t1ons or Levers
11tereate three main functions of levers are :
(a) Ba)ancing
• APPLICATION IN SPORTS

(b) To gain force advantage (c) To gain speed advantage

bmd u the heel IS h Our human leverage system is built for speed and range of movement on applying force. In sports various types
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o(movements require different types of levers, for example, throwing a ball involves levers at the shoulder, elbow
and wrist joints. A few examples of lever application in sports are:
L Cricket Bat (2nd Class Lever) : The fulcrum is the top of the handle, the load is the bat's body, and the force
is closer to the neck of the handle.
1 Kicking- Lower Limb (3rd Class Lever): The fulcrum at the knee joint, force at tibial tuberosity, (attachment
o These type of levers have load (resistance) behveen the effort (force) and the fulcrum. of the quadriceps) load is the foot. •
o In this class of levers, force arm is always the longer of the two, and therefore the force needed to lift 3. Jumping- Plantar Flexion of The Foot (2nd Class Lever): The load is at the toes, the fulcrum is at the heel,
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resisting weight will always be less than the weight. and force is body weight which is anterior to heel.
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QO[ =210 (Biomechanics and Sports) Physical £d11catio11-XII Physical Education-XII
(Biomcchanics and Sports) 211 ~
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 loo\.ing llrfDan or Sldt-to-sldt (1st Cius Lever) : Our head is balan
" "·hkh ri"'lt\ ~n,ilarly "-' a t'll'\'-SolW, ced on our attant
Ooccipit;i1 ..
t,ody or an object to be in static equilibrium it must completely motionless and meet three conditions--
a ~r an,e sum of all the ver~cal forces acting on the body must be zero.
'°'"~ (1) The sum of all the honzontal forces acting on the body must be zero.
'~) Tf't \'auntlf (ii) um of all torques must be zero.
y ') n,es th
I. TIit 1hrtt bai.i<: C\'IITl.-wnt5 of alever are- (iii An object on a level surface is pulled (attracted) downward toward the centre of the earth by e
(1) ML~ ~-ti$hl Ind vclodl)'.
(b) Force. Fulcrum and load
(d) Both (b) and (c)
(CBSE Te.r,baok)
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..~.111ple5: • At the same time, surface forces resist the downward force with equal upward force (called
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f gravity. • • • f 'ntained
ce) The situation 1s one o zero net force and no acceleration For example, stance ma,
(c) Fukrum. R~slalll'e and Effort
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1o, .,; aicket, on th, startiag block by th, sprinte,, wide...., maU>tained by th, w=""• '"·
2. \\'hat is dqlictcd in the picturc1 i,y tfte - 7 --
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(b) 2nd Class lever (c) 3rd Class lever (d)
mic Equilibrium :
(1) 1st aass lever None of the above 2- J:>YI"0ynamic equilibrium was first described by Galileo.
3. Push up is an example of which lever1 (CBSE Tex,book)
(b) 2nd Class lever (C) 3rd Class lever (d) None of the above O 0ynamic Equilibrium can be defined as- a state when all the applied and inertial forces applied to a
(a) Ist Oass lever
o llloving body are in balance, resulting in movement with unchanging speed or direction. In simple words,
4. In the human body. the most common class of lever (CBSE Textbook)
(b) 2nd Class lever (c) 3rd Class lever (d) None of the above 0ynamic equili~~u_m or dyna~ic stability is a balance of the body during movement. ? S~
(a) 1st Class lever
Am. 1-(b), 2-(a), 3-(b),4-(c) To control the equ1hbnum and achieve balance, stability needs to be maximised.
5. Define Lever.
o When the body or an object is moving with a constant velocity, i.e., with no change in speed or direction
(CBSE Textbook) 0
it is said to be in dynamic equilibrium.
6. Draw 3 types of levers used in sports. (CBSE Textbook)
7. With the help of suitable examples, discuss the application of 1st class lever in sports. E,cJJnples: Body position maintained by a sprinter while running on the track, cyclist while cycling, dribbling
(CBSE Textbook)
of the football by a soccer player etc.
8. What do you mean by lever? Explain with the help of diagrams. (CBSE Textbook)
Ill EQUILIBRIUM AND IT'S APPLICATION IN SPORTS !J
A body or object is said to be in equilibrium when, the sum of the forces acting on it is equal to zero,
i.e., there are no imbalancing forces.
Or
Equilibrium is a state of ~st of the body either at stationary or in moving positiov,
In other words, equilibrium is condition in which influence of one force is cancelled by other force; resulting a
stable, balance or unchanging system. In this the resultant of all forces acting on a object or body is zero. Equilibrium
provides us balance and stability. In sports, equilibrium is necessary for performing skills. Guiding Principles to Determine The Degree of Stability
1. Broader the base, the greater the stability : Stability depends upon area of the base. As the base increases,
Types of Equilibrium
the stability increases and vice-versa. For example-
There are two kinds of equilibrium depending on the state of the body: (a) A person standing on toes has very less degree of stability (unstable).
1. Sutic Equilibrium : (b) A person standing on both feet together has little stability.
0 Static equilibrium can be defined as a state when a body is at rest or completely motionless. (c) A person standing with both feet apart has further more stability.
0 Static equilibrium is the balance of the body during rest or stationary position. (d) The person with both hands and feet on the ground has much more stability.
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(e) A wrestler In dl'fensive down position hu ewn more stability. • .reo . •
2.
(f) A penon lying on the floor with arms and feet spread apart has very high stability.
Body weight l1 directly proportional to stability : Tor athlete or an object which weighs
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volleyball,
position . tthplayers
defence e offens1ve
· player.
spread their legs to lower the centre of gravity towards th
~realer Slability. For t:ram11/t, it is difficult to move a heavier person than a lighter one, Comba~ore \vii( ~
Judo, wrestling. taelcwondo, and boxing are played according to the body weight Principle. tive sPotts Ii~
3. lower the centre of gravity, higher the stability : When a player does an activity that need ,
st
player usually lowers their centre of gravity by bending. For aamplt, when a player bends h _s ability, ~
running. he can stop sooner and more efficiently. Similarly, a wrestler . half sits to maintain h·ISJS knees \yL•I
stab·r ,,. e
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1 s hot-put thrower bends his knees in the end so that he may avoid a foul.
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D111.tnce of the centre of gravity of the body above the base : The centre of gravity of a bOd .
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from which the body can have perfect balance It can be considered as the centre of weight of th y IS the Poin
height of the centre of gravity increases, the stability decreases and vice-versa. For example, If st end
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raises his hands upwards, the centre of gravity will move high and stability decreases. a tng Person
s. Directi_on of acting force: During a competition. if the directio~ of an acting/applied force is kno
live sports like wrestling. a wrestler falls on the mat with arms, knees, and legs spread on the mat to
can be increased by moving the line of gravity as close as possible to the edge of the base whe Wn, Stability 0 lll'"°roba
I per balanced position. (This position. makes it difficult for the opposite player to move him).
ex~ed. For aample, when in I judo match the judoka shifts his foot in the line of directto:~ie force is
applied by the opponent to use the force of the opponent as a counterforce to throw him down. the force ,P pro rints track events, athletes need to take an instant start in sprints, they put body weight on their
0 51
(II sh<>~ sphe "Set" position. So, that they can start immediately while balancing their weight. (Initially, e
II CENTRE OF GRAVITY AND IT'S APPLICATION IN SPORTS t,attd O~ t ravity of the body falls on the edge of the baseline of hands.Uthe centre of gravity falls behind e
une,
certtrethengthere will be delay in starting because it will require a greater force to go ahead).
th
th
Centre of gravity is an imaginary point at which all the nws/wei~t of~~ body or object is concentrated,
The centre of gravity of an individual standing in the anatomic position marks the intersecti Te!tY~
primary planes and axes. In humans, the centre of gravity is persistently changing during moveme ~n of three
either within or outside the body depending on the shape and movement of the body. It always :h: It~ be 1 When the sum of force acting upon the object and sum orthe movement acting upon the body is both equal to zero
direction of movement. When the individual stands erect with h_ls~er hand~ at_ the sides, the centre ofif~~ ~
• then the body is said to be in- (CBSE r~xtbook}
located at the level of the hips. The knowledge of centre of gravity 1s very significant for sport perso gr vtty IS (a) Equilibrium (b) Static equilibrium
their skills. ns to better (c) Dynamic equilibrium (d) z.cro force
The ability to balance, whether stationary or moving. is key to success in most sports and physical ... 2. nae position of centre of gravity changes depending upon ii- (CBSE Tarbook}
The stability of an athlete depends on his/her centre of gravity. It is exactly in the middle of the bodacttvtlies. (a) Positionofforce (b) Positionofthebody
which it can rotate freely in any direction and where the weight of the body is centred. y i1l'OUnd (c) Position of intersection of force (d) Position of stability
Examples: 3. Centre of gravity is the average location of an objcct- (CBSE Tatbook}
(a) ln wrestling during snatch and jerk. wrestlers spread their legs
(a) Weight (b) Force (c) Balance (d) Velocity
and lower their body to maintain the stability and makes centre
4. It is a point in body around which the weight is evenly distributed- (DoE}
of gravity come down.
(b) During running. the runner's centre of gravity is in the lower (a) Dynamicequilibrium (b) Staticequilibrium (c) Centrcofgravity (d) Buoyancy
region of the pelvis and in front of his body, because his upper 5, Which of the following will have greater stability-
body is leaning forwards. Having the centre of gravity lower and (a) Spiking position in volleyball (b) Standing stan for 1500 mts. race
in front of his lower body is advantageous for acceleration. (c) Stance of a golfer (d) Tackling in football
Importance and Application of Centre of Gravity in Sports Am, 1-(a). 2-(b), 3-(a),4-(c), 5-(c)
(a) Helps the athlete to move. 6. What do you understand byequilibrium?What are the types of equilibrium? (CBSE Tarbook}
(b) Stops the moving object. 7. Give suitable examples of type ofequilibrium applied to sports/games. (CBSE Ttitbook}
(c) Helps the athlete to accelerate. Define centre of gravity. (CBSE Tatbook}
8.
(d) Helps the athlete in throwing objects. 9. Write down the factors on which the centre ofgravity depends with suitable examples. (CBSE Tatbook)
(e) Helps the athlete to lift the object. (DoE}
10. Explain dynamic equilibrium.
(f) Helps the athlete to pull the object (DoE}
11. What is static equilibrium?
214 (Biomechanics and Sports) ' Physical Educatio11-XII • I JPhysical Educatio11-XII (Biomechanics and Sports) 215 : JO Q
 .,jtl friction: It is the opposing force that comes into play when one body is actually rolling over the
Ill FRICTION AND SPORTS JOl!l•I
und, 11
f\Jrface
0
f the othtt body. Fo, ""•p/,, when• hockey o, <ri<kt b,11 uh;~ ;1 roll, on the wrl,re of
th<
stops after some time due to rolling friction. Such type of friction is very common In games
o
Friction refen to the reslsunce to motion at the contad of two surfaces.
Friction is a force that opposes the motion between tw0 surfaces that are in contact with ea ~
,i,1c1,... • •
frfctiOn.
water,
11
-------
• of ob'I'd>•
sparts• •"'"' w hen motioo
---
• 'Pl'<"<d while1,.,,..1mg through '"Y fl "''d '"ch as- gas,
- ------.:...:_:::__,:::,_..;_ _ _ _ - -..,
o Friction always works in the direction opposite from the direction the object is moving or try~ Other.
10
° Friction also produccs heat, for txamplt, if we rub our hands together quickly, they get warrn ing lllo~.
~
r '"" "'"
,,,,.,fe.' ,ling. O";d frictioo - B " ' . ' - th<_ clot a,d th,,;,. _Thi, 0 why cy, "" o
> ;,~
° 15
Fri~ional force can cause objects in motion to ~me to rest, they act in the opposite dir~0 o wi,,~ cy to""""'
o,;a nction.
n lo ~
strealllhned h•lm•• ,od •p,aally des,goed dothmg
motion. for txamplt, if we roll a ball on a surface, 11 would come to restarter a short while.
Types of Friction
There are three types of friction :
1. Static Friction: It occurs when the force applied to an object does not cause the object to mov • th
of the force. Because of static friction. extra force is required to start the .motion of stationaryem Oebjdil'ettion
---c:'force than the force of static friction between the b·ects' Jor
txamplt, if we try to push a heavy object with les-~
the floor, the o~ject will not move. To make the object move, we have lo exert more force th ~ n d
~ moving, static· fnction
· Once the object starts
stali.c frictaon. • • no Ionger exas • ts• •an the force of
While Paragliding when an athlete glides on air.
0 .. ?
affects fnction.
~MPlvingr
a lubricant between two
.
surfaces. (Motor 0 1•1 grease, and wax).
,
O friction can be reduced by rolling rather than pushing an object.
o friction increases as surfaces are made rougher.
O fridion increases when the force between two objects is increased.
2. Dynamic/J<inetic Friction: Dynamic friction is the opposing force that comes into play when a bod 0
5inooth surfaces produce less friction than uneven surfaces.
moves over the surface of another body. Dynamic friction is of following two types- y actuauy
(al Sliding Friction : Sliding friction is the opposing force that comes into play when one body 15 • ~ethods to Reduce Friction
sliding over the surface of the other body. For example, ~
ice-skating and
__ planting the pole in pol actuauy
_....,;;__.:.....,_...r..::_evauJt fridiOI\ can be reduced by following ways:
0
p0n,hing: Polish and rubbing makes the surface even and smooth. As a result, force of friction gets ~ d .
Speed of....,.
Direction £.g., shining a cricket ball enhances the swing of the ball.
Power of 0
1,ubrication: Use of lubricants such as-motor oil, grease, wax etc. reduces the roughness of the surface, due
......
Direction to which frictional force gets reduced.
0 Use of Wheels and Ball-Bearing: It is easier
to roll an object than to slide it by using wheels and ball-bearings
18 we convert sliding friction into rolling friction. This reduces friction between the two contact surfaces
and
Friction._
Sliding Friction
l helps us to save energy and lime. E.g., in roller skates, both wheels and balls contribute to reducing friction.
streamlining : Friction due to air is reduced by streamlining the shape of the body. E.g., the Javelin, boats,
0
~ ships, 'and vehicles are made with a sharp point to reduce friction.
Speed of...,.
Dlrtttlon Advantages and Disadvantages of Friction in Sports
Powtrof □ friction is essential in the field of sports. Without appropriate friction, sportspersons will not be able to grip any
......
Direction
Friction.,_
sports equipment effectively. The advantages of friction in various sports can be explained as follows:
Advantages of Frictional Force in the Field of Sports
0 ) (J (~ 0 ~, l
L Cricket: Cricket players, especially fielders, wear shoes that have a nails in the bottom. These special types of
Rolling Friclion shoes help to increase the friction force and the players do not slip while running.
;-.___J nOf -
r - , ....J ' .,J IJ
216 (Biomechanics and Spons) P/iyJica/ Educaiion-X/1 .:JJ Physical Education-X/1 (Biomcchanics and Sports) 217
-,
1q
~
I
I
j
 ro;ecnles when thrown follow a curved or parabolic path due to . .
frictional fort"e of the ,
2. B1dminton : B.idminton racket has I knot of clothing that increases the 1 ~ JJI P • ·1e trajectory or parabola. For txamplt, of a when a ball i5 :av•~ho nalthefo~ acting on_it, this~~
P
due lo which the rocket does not slip. -'~w hile the force acting on it(the 'ty). . rown into
.. _,forceofg rav1 1s a Vertical one The ho . . 1t fol.lows is
air. The path
3. B11ketlnll: The frictional force between the playing court and the shoes gives
the player afi . ,tfll'"- tal one,
'.-...it.Of' -ch second is constant, but due to gravity. Is th iJd . =· nzonta1distance tra~lled
ev1ated and it will fall in a curved manner.
not slip. nn Stip OVer the 1,IP-t,all ea . . . ' • pa
ground. During the game, players repeatedly wipe their shoes so that they do :r,,- Id of some sports that mvolve proJ_ectile_ mo~on :
bicycle from sliding. F . .
'- Cydlng: Friction between the bicycle tyres and the road prevents the __ ,_ b
_,-P ..s.,.IL football, shot-put, hammer, discus, 1avehn, golf ball, volleyball• ,"''"113
.
of the bicyd/ct ion for~ a 11, etc. are some objects
present between the brakes and the wheels helps the player in reducing the speed ..
,.....,ct • sm
as projectile
.....keu,.. • sports.
catching or st . 0
S. Footb.tll : In the game of footbalL frictional force helps in throwing away, kicking, Ogu1t •k..tin& ,Id
direction SUdd~PP~g Ifie :i,ody of ,n athlete ads'-'• project;Je during h;gh jump, long jump, gym.,..
.,, di,U,&
football. Apart from this, it is also helps a player to run on the field or change the YWilh<>ut
slipping. • o piJtg etc.
6. Gymnutics : To increase the frictional force between rods and hands, gymnasts
use powder 50 that . : Effecting Projectile Trajectory or Flight Path
thetr
hands do not slip from the rod. ftPO . factors affect projectile trajectory :
stop and changed' . 1ouow1t18 .
7. Running: Friction between the player's shoes and the ground helps the pl~yer to_run. a body or an object. The
U'ection vity: Grav!ty is the for~ of attraction exert~d by the earth to~ards its_centre on
without slipping on the track. If the friction force is less then a player might shp. '(1lt
Gravity affects a projectile as it
better speed can be genera i. Gra the weight of an ob1ect, the greater the influence of gravity upon 1l
8 Athletics: In athletics, the shoes (spikes) are designed to increase friction so that greate~ the height of projectile can obtain. The force of gravity acts on the object
to stop its upward movement
only. Whereas the ,;~-
The shoes used for short-distance running events have spikes in the front position g ded'l?:lls it back to earth, limiting vertical component of the projectile.
distance runner uses completely different shoes.
the ja:elin an~ friction between ~ :esistance : When a pro!ectile moves through air, it is slowed down due to air resistance
acting on it Air
9. Javelin : Friction between the hand and javelin allows the th~wer to grip
shoes and track helps them to generate a perfect ground reaction force for throwing
the Javelin in the .gh 2, ~ tance decreases the honzontal component of a projectile. Though the effect of air
resistance is very less,
l component of a projectile.
n 1 ~ t should be taken into consideration if one wants to increase the horizonta
direction. Without friction. the javelin would just fall out of their hands.
betw~n their feet and the fl00r to :~wing factors deci~e the amount of air resistance on a projectile:
10. Weightlifting : In weightlifting, the weightlifters ~eeds more fricti?n ball, basketball, etc.) is rough, the air
prevent slipping while lifting heavy weights, for which they use speoally designed
shoes. (a) Surface of the Object: Uthe surface of the object (footbalL cricket
sports activities. Hence, We ~ c e will be more..
The friction force is also required for pulling and pushing which is common in all more air resistance will affect the
can say that friction is necessary to give the best performance aU forms of games
and sports. (b) Surface_t~olume Raho: !he larger the surface to volume ratio, the
a golf ball because of
object. For example, a badminton shuttle will have much more air resistance, than
Disadvantages of Frictional Force in Sports the dimples in it.
1. Bicycling: During cycle racing the tires get heated up due to friction. Due to
more heat, tires may burst and is smaller there will be
( ) Mass : Air resistance depends on the mass of the object. If the mass of the object
it may lead to serious accidents. more air resistance.
palm gets damaged due to c more air resistance. For example, a feather in comparison to a stone will have
2. Weightlifting and Gymnastics: In weightlifting and gymnastics, the skin in the (d) Speed ; If speed of an obj~ in~ases, the air ~istance also increases.
This occur; due to friction. For
weight lifters are advised
friction and the athlete even may slip while performing the lift. Hence, gymnasts and example, aspace has more air resistance due to Its speed.
to use powder on their palms and wear special shoes to maintain appropriate friction. depends on the speed of release of the projectile. Uthe
3. Pole-Vault: During Pole-Vault, a vaulter may lose grip on the pole if less friction
is there between palms and 1 Speed of Release: The distance covered by an object if throwing speed is less,
and perform rorrect)y. throwing speed is more, the object rovers maximum distance. On the other hand,
pole. Hence, pole vaulters are advised to use adhesive on the palm to increase friction the object covers less distance.
4. Affects Movements : Any time you want to move an object, friction
can make the job more difficult, as
condition. Angle of Release/Projection : Any object when projected y
movement is directly affected by mass and force applied and also on the surface ' at different angles rovers different distances. The distance
s. Waste of Energy : More friction means more force to overcome it and more force means more energy. Thus, c:overed by an object (implement such a shot, hammer,
energy is wasted due to friction. javelin. etc.) depends on th_e angles of release of p~~e.
g on the nature of
6. uuse Injuries: U a player slides/falls across the ground, he/she can get injured dependin Sc:ientifically, it can be said that the angle of 45 1s the
frictional force. best angle for achieving maximum distance. If an object
no friction, they would
7. Wear and Tear: Sporting equipment wear out with time due to friction. If, there were is projected at the angle of 90°, it does not cover any
last forever. distance but falls on the same spot from where it was
II PROJECTILE IN SPORTS
projected.
5. Height of Release : The higher the level of release, the
fforizantaJ Distance
_
x
greater the distance covered during flight. This~ ~ause u
Projectile the higher the projectile is released, the longer 11 will be
a curved path, suchl,_practicle is . •u
When we throw an object away from the surface of the earth obliquely, it follows in the air.
a projectile. Air resistance of an the ~istance projectile wt
called projectile. G~itational force and air resistance are two forces which act on 6. Spin : The amount and direction of spin acting on a p~ojectile will directly affect
spm.
object depends on the shape of the object and the atmospheric conditions. travel. For example, in tennis shot, topspin rovers less distance as compared to back
~ ., : CJ 218 (Biomechanics and Sports) Physical Educarion-X/1 ctl i i'ftysical Education-Xll (Biomechanics and Sports) 219 JO o•
 Application of Projectile in Sports
~ere are. m~ny sports where projectile motion plays a crucial role. Some of the applications of projectile motion friction force act, in a/an - direction lo lhe direction of IIIOlion ofan object (CBSE TotbookJ
m sports 1s given below:
~
1"' ;,e (b) S... (<) ....._ (d) llopml
1. In Baseball
I
{fl ~followiog • - i,-'""1 mo;,,,""',_ i... ""' (CBS£T""°"'J
0
Pitebing: In basebalL projectile motion is applicable in both throwing and hitting. A thro'_ffl ball undergoes ~... {b) """'1J {<) """' (d) . . . . . . .
projectile motion when it is mid-air since the only force that affects the ball is the acceleration due to gravity. . uon 1sa-
(ti • (CBSE ,,...,.,
A variety of factors will go into the trajectory of a pitch, including a pitcher's height, arm angle, and the spin
being applied to the ball.
fr" """'""' (b) . . , . _ , . . , t,) ~ " " ' (dl C:..,,,,f""'
ttl Id• ,~mon•""'-mor,....,,..,,...,11.....,oan.,,._,Hri<tioo
,i.""' ,cssrn,,..,.,
alibralion (b) Coefficient (c) SlllllOlhncu (d) Descriplioo
(a) C covered by a projectile is called-
~ ,tjrl'CSIS
~. a 'fbepath • tanec
(a) wruc
(b) Trajectory (c) Parabola (d) Javelin
• hof the following angles lhe object thrown will cover the maximum distance-
,J .\
\~

-..._
;"~
.......
"
•1. frOID
(a)
45° (b) 75• (c) 00,
urface of the object is rough. what will be the resistance on it-
•'' If the(.eSS
(a)
s
ligible

(d) 30'
(b) Neither more nor less
(d) More
O Hitting: In terms of hitting. advanced analytics like to use "launch angle" as a good indicator of the optimal (c) N~~I be the distance covered by the object if the initial velocity is less-
angle that a ball should be hit. Launch angle is the angle at which a ball exits the bat as soon as they connect 1, \\'1181 WI (b) Neither men nor less
with each other. The best launch angles, which allow for line drives and home runs, are calculated to be
around 10-30 degrees North of East, relative to the bat. This allows for the most optimal ball flight, usually (,I " " • (~ ""' . .
Negligible nds to move but thetr is
necessary to hit the ball over 325 to 400 feet over the fence. ~) - prod,ttd •"""' ""'""" oll.,obj,<t,°""'• -o(" " ' -"'1 •
,. 1bC fi • moiion between them is known as- (OoE)
2. Basketball no relauve • • (b) Sliding friction
fcfncuon
In the game of basketball, to score a basket, the basketball must be shot at a certain angle with a certain amount (I) Sill I fncuon
Rolling • • (d) Fluid friction
of force. The optimal angle of a shot will vary depending on the height from which the ball is shot and the
player's distance from the hoop. Generally, the ideal angles from the free-throw line varies from 48.7 degrees to (c)
t.(a). 2·(d). J•(c), 4•(b), S·(b), 6-(a). 7•(d), 8-(a). 9-(a)
Nfl, . ·n
52.2 degrees, for shorter players. l)efiOC fncllO .
(CBSE Tr:x1book)
II. What is ,ur•rcs
• ·1·s1ancc?
.
...... (CBSE Tr:x1book}
U, What is limiting friction?
(CBSE Tr:x1book}
12,
l)iscusS van•ous• types of friction. ? (CBSE Tutbook)
"o•;··... ••• •••••••• ...... •··...
k
13. Is fricuon
• advantageous or disadvantageous in games and sports.
~ ~. .. ' . . . (CBSE Tr:t1book}
1'- ggest the methods of rtducmg fncuon.
••·50•
_,.• •••••••••••·· ••· ........
vu
·. ·.
.. .
·. 15, Su
. .
nn.., 00 you undcrsland by friction? Enlist its lypcs.
(CBSE Tt.ttbook)
., "'"" (Do£)
•._ ·.• fri .
···:~ ti rolling and sliding cllOn. (DoEJ
17, De ne dynamic
IL Explain • friction with suiiable examples. (DoEJ
i,. Whal is the difference among static friction. kinetic friction and fluid friction? (DoE)
a How friction is helpful in sports give five suiiable examples? (DoEJ
21. What is friction? Explain its role in spots. (Do£}
22. Define trajectory? (DoE)
23, What is projectile? Explain the factors affecting projectile trajectory? (DoE}
~.,
l... _ 220 (Biornechanics and Sports) Phy.fical £d11catin11·Xll ., ==- /tylkal Education•XII (Biomechanics and Sports) 221 00[~~]
 l (b) 4. (c)
~
5. {b) ( (a)
7. (c) l (b) ,. (b) 10, (al
• f-EXERCISE-t
Objective Type Questions Z [1Ma~
sWer Type Questions
[2·3 Marks Each]
~.mru-1
L •An object in motion will lend lo stay in motion 9. Biomechanics deals with- . ,r,J, examples of the third law of motion.
! ": attY tw0
and an object in rest will tend to stay at rest unless (a) Muscles involved in movement
!i ,.\: ,el iS friction?
acted upon by aforce." Which law is it? (b) Effect of force on different movements done
f' ~ W•"'"•tisdynamicfriction.
I,
(a) Law of inertia (b) l.lw of acreleratioo by human body ,,l.i . •L..Jaill
t>F friction and name its types. (CBS£ 2016)
(c) l.lw of l"l'action (d) None of these
2. 'The motion produced in an object is proportional
(c) To undeistand the physiology of the body
(d) To understand time and distance concept of
·f ~ static friction?
115
/CBS£ 2017)
lo the force exerted on that object.· Which law does J t"h' lain about various types of friction.
~
various movements
this statement l"l'fers to? 10. Read the following statements-Assertion (A) and
s,itll'.~e advantages and disadvantages of friction.
(a) Law ofinertia (b) l.lw of acreleratioo Reason (R). Choose one of the correct alternatives I i'P"' 0,...,..ry evil'. lustily your-Wi~•itabletxampies from 'I"" (CBS£ SQP 211151
(c) I.aw of !'l'action (d) None of these ~venbelow: : f,....die""'"''' law oJ mol"1S wi~ "1mple,. (D.O.E. SQP 2111DI
3. "For every action, the!'l' is always an equal and Assertion (A) : Frictional force is a part of ; If, ~~ics helps lo improv~ technique and equipment of sports. Explain with suitable examples. /Do£)
opposite l"l'action.' Which law does this statement biomechanics. jl, ~ are the three factors which affect projectile trajectory?
~-'IJ1>e Questions /
l"l'fers to? Reason (R) : Biomechanics is the study of forces
(a) Law of inertia (b) Law of acceleration and their effects on the movement ofhuman body. (5 Maril, 1ac111]
(c) Law of !'l'action (d) None of the above In the context of above two statements, which one
u,e meaning and importance of Biomechanics in sports. /Do£)
~ ~ various types of friction? How is friction advantageous or disadvantageous in the field of games
4. _ _ refers to the resistance to motion at the of the following is correct?
contact of two surfaces. (a) Both (A)and (R)are true and (R) is thecorreci
(a) Attraction explanation of (A). i -sports? Explain with suitable ex~mples. /CBS£ 2017)
(b) Friction
(c) Reaction (d) Acceleration (b) Both (A) and (R) are true, but (R) is not the wi,atdo you under u~derstand by_Biomec~ics? Explain its importance with four suitable examples. (Do£)
5. When a gun or pistol is fired, the bullet moves correct explanation of (A). J What are the newt~ns law 0~moti~n? Explain the application of 2nd law of motion in sports. (Do£)
forward. The gun or pistol ~rks backward. This (c) (A) is true, but (R) is false. i WJ,al is friction?Discuss .static, rolling and sliding friction with example. (Do£)
activity indicated which law of Newton? (d) (A) is false, but (R) is true. J wi,at is projectile? Explain the factors affecting projectile trajectory.
(a) Law of reaction (b) Law of action 11. Read the following statements-Assertion (A) and ' With the help of suitable examples, discuss the application of Newton's Laws of Motion in sports.
(c) Law of reaction (d) None of these Reason (R). Choose one of the correct alternatives t /CBS£ Tatbook)
6. Higher the roughness of the surface of the objects, ~venbelow: ffoW can Newton's second law and third law of motion be applied in sports? /CBS£ Tatbook)
the _ _ the frictional force between _lhem. Assertion (A) :Stability is indirectly proportional : Wrftt down the methods of reducing friction and explain any two with suitable example. /CBS£ Tatbook)
(a) Higher (b) l.tsser to the distance of the centre of gravity of the body
above the base.
(c) Equal (d) No change
Reason (R) :For equilibrium to exist the centre of
ease Study Based Questions
7. For every action, there is an equal and opposite
reaction the formally stated Newton's. (Do£) gravity must fall within its base.
(a) First Law (b) Second law In the context of above two statements, which one L l)uring the physical education class Newton's Laws of motion were discussed and their practical application
(c) Third law (d) None of above of the following is correct? in sports events was explained to students. These laws are most relevant in sports as most of the actions in
8. Newton's Isl law of motion is known as _ _. (a) Both (A)and (R) are true and (R) is the correct sports are related to these laws. On the basis of this information answer the following questions.
(Do£) explanation of (A). L Newton's First law of motion is also known as-
(a) Law of Acceleration (b) Both (A) and (R) are true, but (R) is not the (al Law of inertia (b) I.aw of momentum (c) Law of reaction (d) Law ofacceleration
(b) Law of Inertia correct explanation of (A).
1 Newton's second law of motion is also known as-
(c) Law of Action Reaction (c) (A) is true, but (R) is false. (b) The law of inertia
(a) The law of reaction
(d) All of the Above (d) (A) is false, but (R) is true. (d) None of these
(c) The law of acceleration
222 (Biomechanics and Spons) Physical Ed11ca1ion-XII JI P6yJical E'ilucation-X/1 (Biomcchanics and Sports) 22.J
~
•-;1
3. Newton's third law of motion is also know n as-
(a) The law of reaction (b) The law of inertia
(c) The law of acceleration (d) None of these
(DoE)
11• Given below are the different test items:

ques tion-
One the basis of the data, answ er the following
n is being used?
4. In which activity Newton's second law of motio (d) None of Above
(a) Skating (b) Take-off (long jump) (c) Walking
?
5. In which activity flexion and extension takes place (d) Both (b) and (c)
(b) Walking (c) Squats Exercise
(a) Skating
6. In which activity static friction is used? (d) Walking
(a) Skating (b) Take-off (long jump) (c) Push ing Wall
,
Key ~ - - - - - - - - - - - - - - - - - - . . .
- - - - - - - - - - - - - - - - - - i Answer
2. (c) 3. (a) 4. (b) S. (c) 6. (a)
1. (a)

224 (Biomechanics and Sports) Physical Ed11catio11-Xll