Biomechanics And Sports Class 12 Notes

Share with others

Teachers and Examiners (CBSESkillEduction) collaborated to create the Biomechanics and Sports Class 12 Notes. All the important Information are taken from the NCERT Textbook Physical Education (048) class 12.

Contents show

Newton’s Law of Motion & its application in sports

Sir Isaac Newton is one of the greatest scientists and mathematicians and has given three laws of motion. Which are known as Newton’s Three Laws of Motion. These Laws of Motion explain how objects move and how force affects movement. These laws apply to many sports activities like running, jumping, kicking and throwing.

Newton’s First Law (Law of Inertia)

According to the first law, an object will stay still or keep moving in a straight line at the same speed unless a force makes it stop or change direction. Inertia is the resistance of any object to any change in its motion, including a change in direction, objectives to keep moving in a straight line at a constant speed. For example, if you slide a hockey puck on ice, eventually, it will stop because of friction on the ice.

Newton’s Second Law (Law of Momentum)

According to the second law, a force applied to an object is equal to its mass multiplied by its acceleration. The heavy object needs more force to move than a light object. For example, in soccer, a team will require more force to kick the ball high and faster.

Newton’s Third Law (Law of Reaction)

According to the third law, for every action, there is an equal and opposite reaction. It means that if force is applied to an object is pushed back with the same force in the opposite direction. For example, if we need to jump, our legs apply force to the ground, and the ground applies an equal and opposite reaction force (ground reaction force) that propels us into the air.

The lever

The lever is a human body’s mechanism for movement. In our body, bones act like levers and help us to move. All lever systems are made up of four components:

The load: The object that needs to be moved.
The fulcrum: The fulcrum is the joint around which the movement occurs.
The effort: The effort is the muscular force we use to move the object.
The lever: The bones of the skeleton are the levers.

Types of Levers

There are three types of levers:

First-Class Lever
Second Class Lever
Third Class Lever

First-Class Leaver

The fulcrum is in the middle, between effort and load. If the fulcrum is closer to the load, less force is needed, but movement is slower. If the fulcrum is closer to effort, more force is required, but speed increases.

Second Class Lever

A second class lever has the load resistance between the fulcrum and the force. The force arm is always longer than the resistance arm, making it easier to lift heavy objects.

Third Class Lever

A third-class lever has the force between the fulcrum and the resistance. This type of lever is common in the human body, especially in limb movements where speed and flexibility are more important than force.

Application in Sports

Cricket bat (2nd class) – 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.
Kicking – Lower limb (3rd class) – The fulcrum at the knee joint, force at tibial tuberosity, (attachment of the quadriceps) load is the foot.
Jumping – Plantar flexion of the foot (2nd class) – The load is at the toes, the fulcrum is at the heel, and force is your weight which is anterior to your heel.
Looking up/down or side-to-side (1st class) – Your head is balanced on your atlantooccipital joint, which pivots, similarly to a see-saw.

Equilibrium (Stability/ Balance)

Equilibrium means how your body is balanced. Equilibrium helps athletes stay steady while moving, jumping or changing position.

Types of Equilibrium

Equilibrium are divided into two categories:

Static equilibrium.
Dynamic equilibrium.

1. Static Equilibrium

Static equilibrium can be defined as a state when a body is at rest or completely motionless. Static equilibrium is the balance of the body during rest or stationary position. When the body is completely motionless it must meet 3 conditions:

The sum of all the vertical forces acting on the body must be zero
The sum of all the horizontal forces acting on the body must be zero.
The sum of all torques must be zero.

For example, Stance maintained by the batsmen in cricket, on the starting block by the sprinter, wide stance maintained by the wrestler, etc.

2. Dynamic equilibrium

Dynamic Equilibrium can be defined as a state when all the applied and inertial forces applied to a moving body are in balance, resulting in movement with unchanging speed or direction. Dynamic equilibrium or dynamic stability is a balance of the body during movement.

For example, Body position maintained by a sprinter while running on the track, Cyclist while cycling, dribbling of the football by a soccer player etc.

Centre of Gravity

The centre of gravity is the point at which all the weight or mass of a body may be considered to be concentrated. It helps in balance and stability, which is very important for sports and daily movement.

Importance and Application of centre of gravity in Sports

Helps the athlete to move
Stops the moving object
Helps the athlete to accelerate
Helps the athlete in throwing objects.
Helps the athlete to lift the object.
Helps the athlete to pull the object

Example of Centre of Gravity

To get better results and to be strong, the position of the centre of gravity is quite important in many sports, few examples are given below:

In basketball and volleyball the player spreads their legs, which helps to better position against the player.
In wrestling, the wrestler falls on the mat with arms, knees, and legs and spreads on the mat to get a proper balanced position.

Friction & Sports

Friction is a force that opposes the motion between two surfaces that are in touch. Friction always works in the direction opposite from the direction the object is moving or trying to move. Friction also produces heat. For example, if you rub your hands together quickly, they get warmer.

Types of friction

Static friction: It occurs when less force is applied to the heavy object, and the object will not move. You need extra force to move the object. Once the object moves, the static friction will no longer.
Kinetic friction: It occurs when force is applied to an object and the object moves. It includes three different types of friction:
- Sliding friction: Pushing an object across a surface.
- Rolling friction: It occurs between wheels and a surface.
Fluid friction: It opposes the motion of objects travelling through the fluid (gas, air, and water). For example, when you ride a bike, fluid friction occurs between you and the air.

Projectile in Sports

A projectile is an object that moves through the air; it is affected only by gravity and air resistance. If gravity didn’t exist, then the object would keep moving in a straight line. The gravity pulls everything down. A projectile follows a curved path which is known as a parabolic trajectory. Projectiles can help to improve sports performance and help to predict where the object will land. For example, the basketball (object) is thrown to the hoop.