CBSE Class 11 Physical Education Chapter 9: Biomechanics in Sports NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 11 PDF

This chapter delves into the fundamental principles of Biomechanics in Sports, crucial for understanding athletic performance. The NCERT Solutions for Class 11 Physical Education, Chapter 9, provide clear explanations of key concepts. Students will learn about the definition of biomechanics, the laws of motion, the concept of levers, and the importance of equilibrium and center of gravity. The solutions also explain practical applications, such as why athletes lean forward on hills or how different positions affect stability. These solutions are designed to help students grasp the physics behind sports movements, aiding in their exam preparation and enhancing their understanding of athletic techniques.

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Board	CBSE
Class	Class 11
Subject	Physical Education
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 9

Chapter summary

Chapter 9, Biomechanics in Sports, focuses on the application of mechanical principles to human movement in sports. The NCERT Solutions cover definitions of biomechanics, laws of motion, levers, forces, equilibrium, and center of gravity. It explains how these concepts relate to athletic actions, such as starting a race or curling a bicep, and discusses factors influencing stability. This chapter's solutions are essential for students to understand the scientific basis of sports performance.

Learning outcomes

Understand the definition and scope of biomechanics in sports.
Identify and explain Newton's laws of motion.
Define and identify different types of levers.
Explain the concept of force and its role in sports.
Understand equilibrium and its types (static and dynamic).
Explain the significance of the center of gravity for stability.

Topics covered

Paper topics

Biomechanics Definition
Laws of Motion
Newton's First Law (Inertia)
Newton's Second Law (Acceleration)
Newton's Third Law (Reaction)
Levers
Fulcrum, Effort, Load
Types of Levers
Force
Equilibrium (Static and Dynamic)
Center of Gravity
Stability

Important topics

Definition of Biomechanics
Newton's Laws of Motion and their applications
Understanding Levers (Class I, II, III)
Concept of Equilibrium and Stability
Role of Center of Gravity

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Questions and Solutions

Question 1

Define the term biomechanics.

Solution: Biomechanics is defined as the systematic study of the mechanics of body joints. It is also understood as the study of the structure and function of biological systems, particularly in humans, to analyze and understand movement.

Question 2

Name the laws of motion.

Solution: There are three fundamental laws of motion:

The First Law of Motion, also known as the Law of Inertia.
The Second Law of Motion, also known as the Law of Acceleration.
The Third Law of Motion, also known as the Law of Reaction.

Question 3

What is a lever?

Solution: A lever is a rigid bar that is capable of rotating about a fixed point. This fixed point is called the fulcrum.

Question 4

While walking, which law of motion is used?

Solution: While walking, the Third Law of Motion, also known as the Law of Reaction, is used. This is because when we walk, our feet push backward on the ground, and the ground pushes forward on us, propelling us forward.

Question 5

What do you understand by equilibrium?

Solution: Equilibrium is defined as a state of balance or a stable situation. In this state, the net effect of all forces acting on an object is zero, meaning opposite forces cancel each other out, and no changes in motion or position are occurring.

Question 6

What are the different types of equilibrium?

Solution: There are two main types of equilibrium:

Dynamic equilibrium: This occurs when an object is in motion but remains balanced, with forces acting on it canceling each other out.
Static equilibrium: This occurs when an object is at rest and remains balanced.

Question 7

What is a force?

Solution: A force can be defined as a push or pull that one body exerts on another. It is capable of changing the state of motion of an object, deforming it, or both. Mathematically, force is the product of an object's mass and its acceleration.

Question 8

What is centre of gravity?

Solution: The center of gravity is the point within a body or system where the entire weight of the body can be considered to act. It is the point around which the mass or weight of the body is evenly distributed or balanced, and through which the force of gravity acts.

Question 9

Why do we lean forward while climbing up a hill?

Solution: We lean forward while climbing up a hill to keep the center of gravity low. Lowering the center of gravity increases stability, making it easier to maintain balance and ascend the incline.

Question 10

Which law of motion helps an athlete to take a quick start of a 100m race?

Solution: The First Law of Motion, also known as the Law of Inertia, helps an athlete to take a quick start of a 100m race. This law states that an object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. The athlete must overcome inertia to start moving quickly.

Question 11

Which type of lever is used while we curl our biceps?

Solution: A Class III lever is used while we curl our biceps. In this type of lever, the effort is applied between the fulcrum (elbow joint) and the load (weight of the forearm and any object being held).

Question 12

Who will have greater stability?

A fat person or a thin person of same height?
A girl standing in stand at ease position or a girl standing on one leg?

Solution:

A fat person will have greater stability. This is because a larger body mass generally leads to a lower center of gravity and a wider base of support, both of which contribute to increased stability.
A girl standing in a stand at ease position will have greater stability. The stand at ease position provides a wider base of support compared to standing on one leg, which significantly enhances stability.

Common mistakes

Confusing the different laws of motion and their applications.
Difficulty in identifying the class of levers in common movements.
Not fully grasping the relationship between center of gravity and stability.
Misunderstanding the concept of equilibrium in dynamic situations.

Revision tips

Review the definitions of key terms like biomechanics, lever, and force.
Practice identifying which law of motion applies to specific sports actions.
Visualize the fulcrum, effort, and load for different types of levers.
Relate the concept of center of gravity to maintaining balance in various sports stances.

Practice MCQs

Q1. What is the primary definition of biomechanics in the context of sports?

Q2. Which of Newton's laws of motion is also known as the law of inertia?

Q3. What is a lever in biomechanics?

Q4. Which law of motion is primarily applied when an athlete takes a quick start in a 100m race?

Q5. What is the state where opposite forces cancel each other out, resulting in no change?

Q6. When curling your biceps, which class of lever is being used?

Frequently asked questions

What is biomechanics in the context of sports?

Biomechanics is the systematic study of the mechanics of body joints and the structure and function of biological systems, applied to understand and improve athletic performance.

How many laws of motion are there, and what are they called?

There are three laws of motion: the First Law (Law of Inertia), the Second Law (Law of Acceleration), and the Third Law (Law of Reaction).

What is a lever, and what are its components?

A lever is a rigid bar that rotates around a fixed point called the fulcrum. The force applied is the effort, and the resistance to be overcome is the load.

Which law of motion is relevant for taking a quick start in a race?

The First Law of Motion (Law of Inertia) is crucial for a quick start, as it deals with an object's resistance to changes in its state of motion.

What is equilibrium in sports?

Equilibrium is a state of balance where opposing forces cancel each other out, preventing changes in motion or position. It can be static (at rest) or dynamic (in motion).

Why is the center of gravity important for stability?

Maintaining a low center of gravity over the base of support increases stability. Leaning forward when climbing a hill, for example, helps keep the center of gravity low and stable.

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