# NCERT Class 12 Health and Physical Education Chapter 8 Biomechanics and Sports

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## NCERT Class 12 Health and Physical Education Chapter 8 Biomechanics and Sports

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### Biomechanics and Sports

Chapter: 8

MULTIPLE CHOICE QUESTIONS

1. The study and analysis of human movement patterns in sports is called ___________.

(a) sports psychology.

(b) equilibrium.

(c) biomechanics.

(d) none of these.

Ans: (c) biomechanics.

2. Biomechanics is significant in improving ___________.

(a) sports performance.

(b) reducing the risk of injury.

(c) improving technique.

(d) all of these.

Ans: (d) all of these.

3. Which one of the following is not a Law of Motion?

(a) Law of Inertia.

(b) Law of Reaction.

(d) Law of Acceleration.

4. Which is the Newton’s first law of motion?

(a) Law of Acceleration.

(b) Law of Inertia.

(c) Law of Reaction.

(d) none of these.

Ans: (b) Law of Inertia.

5. The force of friction is related to Newton’s __________ law of motion.

(a) First.

(b) Second.

(c) Third.

(d) All of these.

Ans: (a) First.

6. According to Newton’s third law of motion to every action there is always a/an ___________ and opposite reaction.

(a) equal.

(b) unequal.

(c) balanced.

(d) none of these.

Ans: (a) equal.

7. Friction is caused when objects move ___________ each other.

(a) across.

(b) alongwith.

(c) parallel.

(d) none of these.

Ans: (a) across.

8. Study of biomechanics helps to improving ___________.

(a) techniques of sportsperson.

(b) sports equipments.

(c) performance.

(d) all of these.

Ans: (d) all of these.

9. __________ have a centre of gravity.

(a) Individuals.

(b) Objects.

(c) Both (a) and (b).

(d) None of these.

Ans: (c) Both (a) and (b).

10. In basketball which of the following law of motions is implemented?

(a) First law.

(b) Second law.

(c) Third law.

(d) None of these.

Ans: (b) Second law.

STATE WHETHER THE GIVEN STATEMENT IS TRUE OR FALSE

1. Biomechanics is a sub-discipline of physical education.

Ans: True.

2. The study and analysis of human movement patterns in sports is called biomechanics.

Ans: True.

3. Standing position has a larger base of support than a standing position.

Ans: False.

4. When a cricket ball is hit, it rolls on the surface of the ground and finally it stops after some times. This is due to law of reaction.

Ans: False.

5. Stability can be increased by widening the base of support.

Ans: True.

FILL IN THE BLANKS

1. __________ is a necessary evil in sports.

Ans: Friction.

2. Newton’s first law is also called the law of ____________.

Ans: inertia.

3. ___________ can be increased by widening the base of support.

Ans: Stability.

4. The centre of gravity always shift in the direction of ___________.

Ans: movement.

5. At the top of the parabola, the vertical component of the velocity is ___________.

Ans: zero.

ASSERTION AND REASONING

Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R):

Codes: (a) Both (A) and (R) are true and (R) is the correct explanation of (A).

(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).

(c) (A) is true, but (R) is false.

(d) (A) is false, but (R) is true.

1. Assertion (A): Biomechanics is derived from Greek word.

Reason (R): It is the study of the structure and function of biological system.

Ans: (b) Both (A) and (R) are true but (R) is not the correct explanation of (A).

2. Assertion (A): Law of acceleration is the second law of motion.

Reason (R): It states that for every action there is always an equal and opposite reaction.

Ans: (a) Both (A) and (R) are true and (R) is the correct explanation of (A).

3. Assertion (A): There are three types of equilibrium.

Reason (R): Stability is also referred to as movement.

Ans: (d) (A) is false, but (R) is true.

CASE STUDY BASED QUESTIONS

1. Sunny was a good shot putter. His height was 5 feet 6 inches with a body weight of 75 kg. His body was muscular. He used to put the shot with Perie O’brien technique. For the last one year his performance was stable even after his best efforts. He met our new physical educa. teacher to discuss about the root cause of his problem. He saw his technique of putting the shot. He was not satisfied with his technique. He suggested that this technique was not suitable for short-statured individual. He told him to practice disco-put technique instead of Perie O’brien technique. Approximately, after 6 months’ practice, Sunny’s performance was improved by 1.70 metre. In this way, biomechanics helped him a lot.

(A) Biomechanics helps in:

(a) improving technique.

(b) improving designs of sports equipment.

(c) improving teaching and learning.

(d) all the above.

Ans: (d) all the above.

(B) What qualities did Sunny posses?

(a) Learning attitude.

(b) Hard Work.

(c) Both (a) and (b).

(d) None of these.

Ans: (c) Both (a) and (b).

2. A bicycle or car will keep moving unless the rider or driver applies a frictional force through the brakes to stop it. A driver or passenger in a moving car who is not wearing a seat belt will be thrown forward when the car suddenly stops because he remains in motion.

(A) Which one of the following is not the Law of Motion?

(a) Law of Inertia.

(b) Law of Reaction.

(d) Law of Acceleration.

(B) Newton’s second law of motion is also known as:

(a) Law of Acceleration.

(b) Law of Inertia.

(c) Law of Reaction.

(d) None of these.

Ans: (a) Law of Acceleration.

(C) Newton’s first law of motion is also known as:

(a) Law of Reaction.

(b) Law of Acceleration.

(c) Law of Inertia.

(d) None of these.

Ans: (c) Law of Inertia.

3. In biomechanics class, Reshma, the teacher of a private school, brings the students to the physics lab of his school. The students get confused that why she brings all students in a lab. After the completion of the class, they realize the fact because biomechanics is based on Mechanic and Anatomy.

(A) Why does the teacher bring the students to physics lab for biomechanics class?

(a) to explain the principle of Physics.

(b) to explain the law of inertia.

(c) to discuss about law of acceleration.

(d) to explain the law of reaction.

Ans: (a) to explain the principle of Physics.

(B) Biomechanics is associated with

(a) Mechanic.

(b) Physics.

(c) Mechanic and Physics.

(d) Mechanic and Anatomy.

Ans: (d) Mechanic and Anatomy.

(C) Biomechanics is the Science concerned with the:

(a) internal force.

(b) external force.

(c) Both (a) and (b).

(d) none of these.

Ans: (c) Both (a) and (b).

PICTURE BASED QUESTIONS

1. The teachers as well as coaches always make their best efforts to improve the performance of their students in various competitive games and sports. They can help to improve the performance of students if they have adequate knowledge of biomechanics.

(A) The more force one exerts on the downward bounce, the higher the ball bounces into the air. Which law in this statement being referred to?

(a) Newton’s 1st law.

(b) Newton’s 2nd law.

(c) Newton’s 3rd law.

(d) Law of gravitation.

Ans: (c) Newton’s 3rd law.

(B) The acceleration of an object depends directly upon the net force acting upon the object and inversely upon the object’s

(a) Weight.

(b) Mass.

(c) Height.

(d) Density.

Ans: (b) Mass.

(C) The study of human body and various forces acting on it is

(a) Biology.

(b) Biomechanics.

(c) Physiology.

(d) Anatomy.

Ans: (b) Biomechanics.

OBJECTIVE TYPE QUESTIONS

Q. 1. How is frictional force helpful in football game?

Ans: In the game of football, frictional force helps in throwing away, kicking, catching or stopping the football. Apart from this, it is also helps a player to run on the field or change the direction suddenly without slipping.

Q. 2. What is a friction?

Ans: It is defined as the resistance to motion which is created by contact between two surfaces. This resistance to motion is called the force of friction.

Q. 3. What do you mean by biomechanics?

Ans: Biomechanics is subdiscipline of physical education.

Q. 4. Name two types of equilibrium.

Ans: (i) Static equilibrium.

(ii) Dynamic equilibrium.

Q. 5. What is ‘dynamic’ friction’?

Ans: Dynamic friction is the opposing force that comes into play when one body is actually moving over the surface of another body. Dynamic friction may be of two types, i.e. sliding friction and rolling friction.

Q. 6. Enlist the methods of reducing friction.

Ans: Methods of reducing friction are:

(i) Polishing.

(ii) Lubrication.

(iii) Use of ball bearings.

(iv) Streamlining.

Q. 7. Define equilibrium.

Ans: Equilibrium is condition in which influence of one force is cancelled by other force; resulting a stable, balance or unchanging system.

Q. 8. What is the first law of Newton?

Ans: This law states that a body at rest will remain at rest and a body in motion will remain in motion at the same speed and in the same direction till any external force is applied on it to change state.

Q. 1. Enumerate the laws of motion.

Ans: The three laws of motion are:

(i) Newton’s First Law of Motion: This law is also known as law of inertia.

This law states that a body at rest will remain at rest and a body in motion will remain in motion at the same speed and in the same direction till any external force is applied on it to change that state.

(ii) Newton’s Second Law of Motion: This law states that the acceleration of an object is directly proportional to the force producing it and inversely proportional to its mass.

(ii) Newton’s Third Law of Motion: This law states that to every action, there is always an equal and opposite reaction. This law describes what happen to a body when it exerts a force on another body.

Q. 2. “Friction is a necessary evil.” Justify your answer with suitable examples from sport.

Ans: Friction is usually called a necessary evil. It means that it is essential in games and sports. Without friction, we cannot give a better performance in the field of sports.

Examples are spikes used by athletes for running and studs used in football boots of the players. However, friction has disadvantages also. In cycling, there should not be more friction between road and the tyres of the cycle.

Q. 3. Elucidate the types of friction.

Ans: The force acting along two surface in contact which opposes the motion of one body over the others is called the force of friction. It is very important in sports. The larger the area of contact between the surfaces, the greater is the force of friction. When both the surfaces are smooth, the force of friction reduces to almost zero.

Two types of friction are:

(i) Static Friction: The opposing force that comes into play when one body tends to move over the another surface but the actual motion has not yet started.

(ii) Dynamic Friction: It is friction between two surfaces that are in relative motion with respect to each other. It is the opposing force that comes into play when one body is actually moving over the surface of another body. Dynamic friction may be of two types, i.e., sliding friction and rolling friction.

Q. 4. How Newton’s second law and third law of motion can be applied in sports?

Ans: Second laws: If a baseball player hits a ball with double the force, the rate at which the ball will accelerate (speed up) will be doubled, Football players can slow down, stop, or reverse the direction of other players depending upon how much force they can generate and in which direction.

Third Law: A swimmer propels herself through the water because the water offer enough counter force to oppose the action of her hands pushing, allowing her to move. An athlete can jump higher off a solid surface because it opposes his body with as much force as he is able to generate, in contrast to sand or other unstable surface.

Q. 5. Describe two types of equilibrium.

Ans: There are two types of equilibrium:

(i) Dynamic Equilibrium: The maintenance of body balance during various body movements is called dynamic equilibrium. That motion is considered a prime element in sports and in order to perform well and achieve success, maintenance of dynamic equilibrium is very important.

(ii) Static Equilibrium: A position or state of equilibrium in stationary position is called static equilibrium. The centre of body must fall within its base in order to achieve static equilibrium.

Q. 6. What is the disadvantage of friction in sports?

Ans: Friction is also the reason for decreased speed of playing objects on ground as well, due to resistance by uneven ground. Sliding or movement of fallen person causes increased injury due to friction, as it causes heat and resistance to movement of body. Wear and tear of ball and other objects is also a common example.

Disadvantages of friction is as follows:

(i) Air resistance has disadvantages to ball games, where speed of ball reduces due to the friction. Example in football, badminton, cricket etc.

(ii) Friction is also the reason for decreased speed of playing objects on ground as well, due to resistance by uneven ground.

(iii) Sliding or movement of fallen person causes increased injury due to friction, as it causes heat and resistance to movement of body.

(iv) Wear and tear of ball and other objects is also a common example.

(v) Playing spaces are made as smooth as possible to avoid resistance and hence friction.

Q. 1. What are the importance of biomechanics in sports?

Ans: Importance of biomechanics in sports:

(i) Improves performance in sports: Principles of biomechanics tell us about right techniques, effective and result oriented posture to get more efficient results by applying minimum muscular force which in turn improves performance in sports.

(ii) Improvement in technique: A sportsperson’s performance can be improved by improving her/ his technique. The application of biomechanical principles can be applied to improve technique in two ways. First, the coaches may use their knowledge of biomechanics to rectify the errors made by the sportsperson in order to improve the execution of a skill. Second, the sportsperson may discover a new and more effective technique for executing a sports skill.

(iii) Development of improvement of sports equipment: The principles of biomechanics are used to modify the sports equipments. For example, tee shirts, studs, spikes, swimming costumes, hockey sticks, different size footballs and low weight helmets for protection.

(iv) Improvement in training techniques: A teacher can analyze the player’s movement or action with the help of the biomechanical principles. It helps in improving the training techniques which helps us to get more results.

(v) Prevents sports injuries: It helps to find out the factors or the forces that can lead to the injuries during the game situation. It also helps in prevention of the sports injury.

(vi) Helps in understanding human body: It gives the knowledge of different systems of our body. For example, nervous system, muscular system and skeletal system.

Q. 2. What is Projectile? Explain the factors affecting projectile trajectory?

Ans: Projectile: An object thrown into the space either horizontally or an acute angle under the action of gravity is called a projectile. There are forces which act on a projectile gravitational force and air  resistance. Air resistance of an object varies greatly and it depends on the object’s particular shape and the atmospheric conditions in which the object is released.

The factors affecting Projectile Trajectory are mentioned below:

(i) Angle of projection: An object which is projected at different angles covers different distances. When it is projected or released at angle of 30, making it a parabolic path and covers lesser distance. When it is projected at 60, it covers a distance less that 30. When it is released at an angle of 45, makes a parabolic path and covers maximum distance. So the distance covered by an object (short-put, hammer, javelin, discus etc. depends on the angle of release of projectile)

(ii) Height of release: The higher the level of release, the greater distance is covered in flight, this is because the higher projectile is released. The longer it will be in the air. The horizontal component will be acting on the projectile for longer.

(iii) Speed of release: The speed or 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 length of flight time and therefore the distance covered. This would be an advantage in sports which primarily requires good distance in long jump, sky jump etc.

(iv) Gravity: Gravity acts on a body or object to give it mass. The greater the weight of an object, the greater the influence of gravity upon it. Gravity will effect a projectile as well as it will decrease the height, the projectile can obtain. For example:- a cricket ball can be thrown at greater distance in comparison to shot put.

(v) Air Resistance: When a projectile moves through the air, it is slow down by an air resistance. Air resistance decreases the horizontal component of a projectile. The effect of air resistance is very small but it need to be taken into consideration if you want to increase the horizontal components of a projectile. The factors are related to the amount of air resistance acting on a projectile-mass, surface of the object, surface of the volume ratio. Trajectory Initial Horizontal Velocity Vertical Component Initial Vertical Velocity Horizontal Component.

(vi) Spin: The amount and direction of spin acting on a projectile will directly effect the  distance while travel.

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