UNIT 8 Biomechanics and Sports XII

 UNIT 8 Biomechanics and Sports  XII

 Biomechanics and Sports

1. Newton’s Law of Motion & its application in sports 

2. Types of Levers and their application in Sports. 

3. Equilibrium – Dynamic & Static and Center of Gravity and its  application in sports 

4. Friction & Sports 

5. Projectile in Sports 

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Biomechanics and Sports

Biomechanics is the scientific study of the mechanics of human movement. It involves the analysis of forces and their effects on the body during various physical activities and sports. By applying principles of physics, engineering, and biology, biomechanics helps in understanding how the human body moves and how performance can be improved while reducing the risk of injuries.

Definition of Biomechanics

Biomechanics is the study of the structure and function of biological systems (like humans) using the methods and principles of mechanics. In sports, it is used to enhance technique, equipment design, and training strategies.

Importance of Biomechanics in Sports

  1. Performance Improvement: Helps athletes optimise their movements and techniques for better efficiency and effectiveness.
  2. Injury Prevention: Identifies movements or postures that might cause injuries and provides corrective measures.
  3. Equipment Design: Assists in designing sports equipment (like shoes, rackets, or helmets) to improve comfort and performance.
  4. Understanding Human Motion: Analyses how different muscles, joints, and bones work together during various physical activities.

Applications of Biomechanics in Sports

  • Technique Analysis: Evaluates and refines an athlete's technique in activities such as running, swimming, or throwing.
  • Sports Training: Develops training methods tailored to the athlete’s biomechanics.
  • Rehabilitation: Aids in designing recovery exercises for athletes post-injury.
  • Sports Performance: Assists coaches and athletes in identifying and correcting biomechanical inefficiencies.

Examples in Sports

  1. Running: Analysing stride length and foot placement to improve speed and endurance.
  2. Swimming: Evaluating stroke techniques to minimise water resistance and maximise propulsion.
  3. Cricket/Bowling: Studying the angle of delivery and body movement to avoid overuse injuries.
  4. Weightlifting: Ensuring correct posture and lifting techniques to avoid strain on joints and muscles.

Conclusion

Biomechanics bridges the gap between science and sports. It provides invaluable insights into human movement, helping athletes achieve peak performance while maintaining their health and safety. Through biomechanics, sports continue to evolve, becoming more efficient and injury-free.

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1: Newton’s Laws of Motion and Their Application in Sports

Sir Isaac Newton's three laws of motion form the foundation of mechanics and have significant applications in sports. These laws explain how forces interact with the motion of objects, including athletes and equipment, to produce various outcomes in sports activities.

1. Newton’s First Law of Motion (Law of Inertia)

Statement: An object at rest remains at rest, and an object in motion continues in uniform motion in a straight line unless acted upon by an external force.

Application in Sports

  • Start of a Race: A sprinter remains stationary at the starting line until the external force (their push-off against the ground) propels them forward.
  • Soccer Ball: A stationary ball will not move until it is kicked, and a moving ball will stop due to friction or when a player intercepts it.
  • Archery: The arrow remains at rest on the bowstring until the archer applies force by releasing the string.

2. Newton’s Second Law of Motion (Law of Acceleration)

Statement: The acceleration of an object is directly proportional to the net force applied and inversely proportional to its mass. Mathematically, F=maF = ma, where FF is force, mm is mass, and aa is acceleration.

Application in Sports

  • Throwing and Hitting: A cricket ball thrown with greater force accelerates more than a lighter or less forceful throw.
  • Weightlifting: The greater the force exerted by a weightlifter, the more acceleration they can give to a heavy barbell.
  • Tennis: The speed of the tennis ball depends on the force of the racket swing and the mass of the ball.

3. Newton’s Third Law of Motion (Action and Reaction)

Statement: For every action, there is an equal and opposite reaction.

Application in Sports

  • Running: When a runner pushes against the ground, the ground exerts an equal and opposite force that propels the runner forward.
  • Swimming: A swimmer pushes water backward with their hands and legs, and the water pushes them forward with an equal force.
  • Basketball: When a basketball player jumps, they push down on the ground, and the ground pushes them upward with an equal and opposite force.

Practical Examples of Newton’s Laws in Sports

  1. Cycling:

    • First Law: The bicycle remains stationary unless pedaled.
    • Second Law: The harder the cyclist pedals, the faster the acceleration.
    • Third Law: The tires push against the ground, and the ground pushes the bicycle forward.

  2. Football (Soccer):

    • First Law: A ball keeps moving until a player stops it or it encounters resistance.
    • Second Law: The stronger the kick, the greater the acceleration of the ball.
    • Third Law: When a player kicks the ball, the ball exerts an equal force on the foot.

  3. High Jump:

    • Third Law: The athlete applies force against the ground to propel themselves upward.

Conclusion

Newton’s laws of motion are fundamental in understanding the mechanics of sports movements. Athletes and coaches can use these principles to refine techniques, improve performance, and minimise injuries. Whether it's running, swimming, cycling, or ball games, these laws govern all sports activities.

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2: Types of Levers and Their Application in Sports

A lever is a simple machine that consists of a rigid bar (the lever arm) that rotates around a fixed point called the fulcrum. Levers are used to amplify force or change the direction of motion, and they are classified into three types based on the position of the fulcrum, effort, and load.

The three types of levers are:

1. First-Class Lever (Fulcrum Between Effort and Load)

  • Structure: The fulcrum is located between the effort (force applied) and the load (resistance).
  • Mechanical Advantage: It can either amplify force or change the direction of the applied force.

Examples in Sports:

  1. Seesaw: In sports, the action of a seesaw can be compared to how a person might balance their body or use equipment with the fulcrum between the body and the applied force (like in some balance exercises).
  2. Crowbar: A crowbar used in lifting a heavy object also acts as a first-class lever where the fulcrum is at the middle.

In Sports:

  • Triceps during a push-up: When performing a push-up, the elbow joint acts as the fulcrum, the triceps apply the effort, and the body’s weight is the load. This setup makes it easier to lift the body off the ground.

2. Second-Class Lever (Load Between Fulcrum and Effort)

  • Structure: The load is placed between the fulcrum and the effort.
  • Mechanical Advantage: It amplifies force, allowing a smaller effort to move a larger load.

Examples in Sports:

  1. Wheelbarrow: When lifting a wheelbarrow, the wheel (fulcrum) is at the rear, the load is in the container, and the effort is applied at the handles.

In Sports:

  • Calf Raise: In the calf raise exercise, the ball of the foot acts as the fulcrum, the body’s weight is the load, and the calf muscles provide the effort to lift the body upward.
  • Jumping (e.g., high jump or long jump takeoff): The foot acts as the fulcrum, the force applied by the leg muscles is the effort, and the body’s weight is the load to be lifted off the ground.

3. Third-Class Lever (Effort Between Fulcrum and Load)

  • Structure: The effort is located between the fulcrum and the load.
  • Mechanical Advantage: This type of lever sacrifices force for speed and distance, allowing for rapid movement.

Examples in Sports:

  1. Tongs: Tongs used to grab or flip objects have the effort applied between the fulcrum and the load (the object being picked up).

In Sports:

  • Biceps in Arm Flexion: When you bend your elbow (as in a bicep curl), the elbow joint acts as the fulcrum, the biceps apply the effort, and the hand/weight is the load. This allows quick, forceful movement.
  • Kicking a Football: In a soccer kick, the hip joint acts as the fulcrum, the muscles in the thigh provide the effort, and the ball is the load being kicked.
  • Batting in Cricket or Baseball: When a batter swings the bat, the elbow is the fulcrum, the muscles of the forearm exert the effort, and the bat strikes the ball, which is the load.

Conclusion

Levers play an essential role in sports as they enhance an athlete’s ability to generate force, move objects, and improve efficiency. Understanding how different types of levers work can help athletes optimise their movements and techniques, whether it's for lifting weights, running, jumping, or swinging a bat. Each type of lever has its specific advantages and applications that make certain movements more effective in sports performance.

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3: Equilibrium – Dynamic & Static and Centre of Gravity and Its Application in Sports

Equilibrium refers to a state of balance where the forces acting on an object are equal and opposite, resulting in no movement or a constant speed. It is a key concept in both sports performance and injury prevention. The two main types of equilibrium are static equilibrium and dynamic equilibrium, both of which play vital roles in sports.

1. Static Equilibrium

  • Definition: Static equilibrium occurs when an object is at rest, and the forces acting on it are balanced. In this state, there is no motion, and the object remains stationary.
  • Condition: The sum of all forces and the sum of all torques (moments) acting on the object must be zero.

Application in Sports:

  • Yoga and Gymnastics: A gymnast or a yoga practitioner holding a pose (e.g., a handstand) is an example of static equilibrium. They must maintain a balanced position, where the force of gravity pulling them down is counteracted by the muscular effort keeping them in place.
  • Shooting in Archery: When an archer takes aim and holds the bow steady before releasing the arrow, their body remains in a state of static equilibrium, ensuring stability and accuracy.

2. Dynamic Equilibrium

  • Definition: Dynamic equilibrium occurs when an object is in motion, but the forces acting on it are balanced, resulting in constant velocity or motion without acceleration. In this state, the object may be moving in a straight line or rotating.
  • Condition: The sum of all forces is zero, but the object is in motion.

Application in Sports:

  • Running: A runner achieves dynamic equilibrium when their body is in motion, but the forces involved in their movement (e.g., the force from their legs and the ground reaction force) are balanced, allowing them to move at a constant speed without falling.
  • Cycling: A cyclist maintains dynamic equilibrium by balancing the forces of pedalling and resistance (from wind or terrain) while staying upright on the bike.
  • Diving: In a diving event, a diver achieves dynamic equilibrium when rotating in the air, as the forces from gravity and the diver’s muscle movements are balanced during the aerial flip or twist.

3. Centre of Gravity (CG)

  • Definition: The centre of gravity (CG) is the point in a body or object where its entire weight can be considered to act. It is the balance point where an object remains stable when supported.
  • In Humans: The CG is located slightly above the pelvis, near the belly button, but it can change depending on body position.

Factors Affecting the Centre of Gravity:

  • Body Shape: A person with a wider stance has a lower CG and greater stability.
  • Movement: When the body moves, the CG shifts accordingly. For example, when an athlete jumps or leans, their CG changes.

Application of Centre of Gravity in Sports

  1. Balance and Stability:

    • Gymnastics: Gymnasts must keep their CG within their base of support (hands or feet) to maintain stability and perform precise movements.
    • Wrestling and Judo: Athletes maintain a low CG and wide stance to increase their stability and avoid being thrown off balance by an opponent.

  2. Leaping and Jumping:

    • High Jump: In the high jump, athletes adjust their CG to clear the bar by curving their bodies and shifting their CG above the bar while in the air.
    • Long Jump: The athlete must control their CG during takeoff, flight, and landing to achieve maximum distance.

  3. Sports Equipment:

    • Pole Vaulting: The vaulter's ability to control their CG with the pole helps them clear the bar. A pole that bends in a controlled manner allows them to adjust their CG for a successful jump.
    • Skiing and Snowboarding: Skiers and snowboarders shift their CG for balance and stability on the slopes. Leaning forward or backward helps them steer and control speed.

  4. Increased Mobility:

    • Football (Soccer): A football player can change direction quickly by lowering their CG and shifting their weight to one foot, allowing for swift movements like dribbling and dodging opponents.
    • Basketball: Players lower their CG during defensive stances or while attempting to make a quick pivot to avoid defenders.

  5. Diving and Swimming:

    • Diving: Divers adjust their body position to control their CG during aerial flips and twists, ensuring they enter the water correctly.
    • Swimming: The swimmer's body position, with a balanced CG, is crucial for minimizing drag and maximizing speed in the water.

Conclusion

Understanding equilibrium and the centre of gravity is crucial for athletes across all sports. Achieving the right balance—whether at rest or in motion—enables better performance, greater stability, and reduced risk of injury. By learning to control their body’s CG and applying the principles of equilibrium, athletes can improve their technique, agility, and overall athletic ability.

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4: Friction and Its Application in Sports

Friction is the force that resists the relative motion or tendency to such motion of two surfaces in contact. It plays a significant role in sports, influencing performance, safety, and technique. Friction can be both beneficial and detrimental, depending on the situation and the type of sport.

Types of Friction:

  1. Static Friction:

    • Definition: Static friction is the frictional force that resists the initiation of sliding motion between two surfaces in contact.
    • Application in Sports:
      • Starting Movement: Static friction helps athletes start their movement, such as when a sprinter pushes off the starting blocks or when a football player gains traction to sprint on the ground. Without static friction, these movements would be impossible to initiate.
      • Grip in Tennis or Badminton: The shoes of players provide static friction, allowing them to make quick stops and changes in direction.

  2. Kinetic (Dynamic) Friction:

    • Definition: Kinetic friction is the frictional force that acts between two surfaces that are sliding past each other.
    • Application in Sports:
      • Slowing Down Movement: Kinetic friction helps in slowing down a player’s movement, as seen in skiing, where friction between the ski and snow reduces the speed after a high-speed run.
      • Rugby and American Football: Players use kinetic friction to their advantage when slowing down or changing direction on the field.

  3. Rolling Friction:

    • Definition: Rolling friction occurs when an object rolls over a surface, as opposed to sliding.
    • Application in Sports:
      • Wheel Sports: In cycling or skateboarding, rolling friction between the wheels and the surface is crucial for controlled movement. The design of the tires or wheels is optimized to minimize rolling friction for maximum speed.

Benefits of Friction in Sports:

  1. Traction and Grip:

    • Running and Sprinting: Sprinters rely on friction between their shoes and the track to push off effectively. Special track shoes are designed to maximize friction to achieve better acceleration and speed.
    • Football, Basketball, and Rugby: Players need traction from their footwear to make quick cuts, pivots, and to prevent slipping. Cleats, for example, are designed to increase friction with the ground.
    • Cycling: The friction between the tires and the road surface is necessary for control and speed regulation.

  2. Control:

    • Tennis: Tennis players rely on the friction between the racket strings and the ball to control the spin and direction of the ball.
    • Golf: The friction between the golf club and the ball allows the golfer to apply spin, affecting the ball's trajectory and bounce.

  3. Stability:

    • Skiing: Skiers use the friction between the skis and snow to maintain control, slow down, and make turns.
    • Ice Skating: Though ice skating involves lower friction compared to other sports, the friction between the skates and the ice surface is essential for stopping, starting, and maneuvering.

Negative Effects of Friction in Sports:

  1. Increased Wear and Tear:

    • Tennis and Badminton Rackets: The friction between the strings of the racket and the ball can cause the strings to wear out over time. In addition, the surface of the court can also wear out footwear.
    • Running Shoes: Continuous friction between the shoe and the ground can wear down the soles of the shoes, leading to reduced grip and potential slipping.

  2. Heat Generation:

    • Chafing and Blisters: In activities like running or cycling, friction between the skin and clothing or equipment can lead to chafing and blisters.
    • Rugby and Football: The constant rubbing of skin against equipment or the ground can cause abrasions, which may hinder an athlete’s performance.

  3. Slipping and Lack of Traction:

    • On Wet Surfaces: On a wet or icy surface, insufficient friction can cause athletes to slip, leading to falls or injuries.
    • In Sports like Football or Hockey: Poor friction on certain playing surfaces, such as wet grass or ice, can lead to reduced control, making it harder to change direction or stop suddenly.

Controlling Friction in Sports:

  1. Footwear:
    • The design of sports footwear is a critical factor in managing friction. For example, basketball shoes have specially designed soles to enhance grip on the court, while track shoes with spikes offer superior traction on running surfaces.
  2. Surface Design:
    • Sports surfaces like tracks, courts, and pitches are designed to provide optimal friction for specific sports. For example, a basketball court’s wooden floor is polished to provide a balance between enough grip and minimal wear.
  3. Lubrication and Technology:
    • In sports like cycling, some athletes apply lubricants to reduce friction between the moving parts of their equipment (e.g., bike chains) to enhance speed and efficiency.
  4. Specialized Sports Equipment:
    • Skiing: Ski wax is applied to reduce friction between the skis and snow, allowing athletes to glide more easily while maintaining control.
    • Swimming: The friction between the swimmer’s body and the water can be reduced by wearing specialized swimsuits designed to minimize drag.

Conclusion

Friction plays a fundamental role in sports performance, from providing necessary traction to controlling speed and stability. It can be a force for good when used appropriately, allowing athletes to excel in their chosen sport. However, if not managed properly, friction can lead to unwanted side effects such as injury or reduced performance. Understanding and optimizing friction in both equipment and body movements is essential for athletes across all levels.

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5: Projectile in Sports

In sports, a projectile is any object that is thrown, kicked, or hit into the air and follows a curved path under the influence of gravity and air resistance. The concept of projectile motion is an essential aspect of many sports, as it governs the trajectory, distance, and speed at which objects such as balls, javelins, discus, and even players themselves move through the air.

Key Concepts of Projectile Motion

Projectile motion is the motion of an object thrown or projected into the air, influenced by the following:

  1. Initial Velocity: The speed and direction at which the object is thrown or launched. This determines how high and how far the projectile will travel.

  2. Angle of Launch: The angle at which the object is launched relative to the horizontal. This plays a critical role in determining the range and maximum height of the projectile.

    • Optimal Angle: For maximum range in most sports, an angle of 45° is ideal, though this can vary depending on the specific conditions (e.g., wind or air resistance).

  3. Acceleration due to Gravity: Gravity constantly pulls the projectile downward, which affects its vertical velocity and the height it reaches before coming back down.

  4. Air Resistance: The force that opposes the motion of the projectile through the air. The effect of air resistance can vary depending on the shape and size of the object.

Factors Affecting Projectile Motion in Sports

  1. Speed: The greater the speed at which a projectile is launched, the farther and higher it will travel. For example, in baseball, the speed of the pitch determines the trajectory of the ball.

  2. Launch Angle: The angle at which a projectile is launched significantly impacts its flight path.

    • Low Angles: Low-angle launches (e.g., 10° to 20°) typically result in shorter distances but faster speeds (e.g., in a sprinting start or low shots in football).
    • High Angles: High angles (e.g., 45° or above) result in greater heights but reduced distances (e.g., in long jumps or high throws).

  3. Height of Launch: The height from which the projectile is launched influences how long it stays in the air and its overall trajectory. For example, a javelin thrown from a higher position may travel farther than one thrown from a lower height.

Applications of Projectile Motion in Sports

1. Football (Soccer)

  • Kick: When a football is kicked, it becomes a projectile. The angle at which it is kicked and the speed of the kick determine the trajectory, distance, and accuracy of the ball's flight.
  • Free Kicks: A player must adjust the angle and speed to navigate obstacles (e.g., defenders) and aim for the goal.

2. Cricket

  • Bowling: A bowler in cricket launches the ball into the air with a particular speed and angle. The combination of these factors, along with spin, can influence how the ball bounces and its final trajectory.
  • Batting: When a batter hits the ball, the ball follows a projectile motion path, and the angle and force of the hit determine how far the ball travels.

3. Tennis

  • Serve: A tennis serve is a prime example of projectile motion. The speed, spin, and angle of the racket’s impact with the ball determine the ball's trajectory and its interaction with the opponent’s court.

4. Basketball

  • Shooting: When a player shoots a basketball, the ball follows a parabolic trajectory. The release angle and speed are critical in determining whether the ball will go through the hoop.

5. Javelin, Shot Put, and Discus

  • Throws: Athletes in track and field events such as javelin, shot put, and discus need to control the angle, speed, and trajectory of their throws to achieve maximum distance. Each type of throw has specific angles and techniques for optimal performance.

6. Volleyball

  • Serve and Spike: In volleyball, both the serve and the spike involve launching the ball in the air. The trajectory is affected by the angle at which the ball is hit and the speed.

7. Golf

  • Tee Shots and Putting: When a golfer hits the ball, it becomes a projectile. The angle of launch, combined with the force applied, determines how far the ball will travel and how it will interact with the course.

8. Golf

  • Tee Shots and Putting: When a golfer hits the ball, it becomes a projectile. The angle of launch, combined with the force applied, determines how far the ball will travel and how it will interact with the course.

Projectile Motion Equations

The motion of a projectile can be described using basic physics equations. The most important equations governing projectile motion are:

  1. Horizontal Motion:

    Distance(R)=v2sin⁡(2θ)g\text{Distance} (R) = \frac{v^2 \sin(2\theta)}{g}

    Where:

    • vv is the initial velocity
    • θ\theta is the launch angle
    • gg is the acceleration due to gravity

  2. Vertical Motion:

    h=vy⋅t−12gt2h = v_y \cdot t - \frac{1}{2} g t^2

    Where:

    • vyv_y is the vertical component of the initial velocity
    • tt is the time in the air
    • gg is the acceleration due to gravity

Conclusion

Understanding the principles of projectile motion is crucial in various sports as it allows athletes to optimize their performance. By manipulating factors such as speed, angle, and height, players can control the trajectory of the ball or object they are handling, enhancing their chances of success. Whether it’s a soccer player trying to score a goal, a javelin thrower aiming for distance, or a tennis player serving effectively, the concepts of projectile motion apply directly to sports strategy and technique.

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