CBSE Class 11 Physical Education: Chapter 9 Biomechanics and 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 and its application in sports, crucial for Class 11 Physical Education students. The NCERT Solutions provide clear explanations for concepts like the laws of motion, levers, force, equilibrium, and center of gravity. Understanding these principles helps athletes analyze movements, improve performance, and prevent injuries. The solutions cover definitions, applications of Newton's laws in sports scenarios, and factors affecting stability. This resource is designed to aid students in grasping complex biomechanical concepts, answering short-answer questions effectively, and preparing for their examinations by reinforcing theoretical knowledge with practical examples from sports.

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Quick info

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

Chapter summary

Chapter 9, 'Biomechanics and Sports,' focuses on the application of mechanical principles to human movement in physical activities. The NCERT Solutions cover essential topics including the definition of biomechanics, Newton's laws of motion and their relevance in sports, the concept of levers and their classes, forces, equilibrium (static and dynamic), and the center of gravity. The solutions also address practical applications like maintaining stability while walking or climbing and analyzing common sports actions.

Learning outcomes

Understand the definition and scope of biomechanics in sports.
Identify and explain Newton's laws of motion and their application in athletic performance.
Define and differentiate between various types of levers used in the human body.
Explain the concepts of force, equilibrium, and center of gravity.
Analyze how biomechanical principles contribute to stability and movement in sports.
Relate biomechanical concepts to everyday actions and athletic scenarios.

Topics covered

Paper topics

Definition of Biomechanics
Laws of Motion (Newton's Laws)
Law of Inertia
Law of Acceleration
Law of Reaction
Levers
Force
Equilibrium (Static and Dynamic)
Center of Gravity
Stability in Sports
Application of Biomechanics in Sports

Important topics

Definition and scope of Biomechanics
Newton's Laws of Motion and their sports applications
Levers in the human body
Center of Gravity and Stability
Equilibrium concepts

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Questions and Solutions

Question 1

Define the term biomechanics.

Solution: Biomechanics is the scientific discipline that applies the principles of mechanics to study the structure and function of biological systems, particularly focusing on the human body's movement and the forces acting upon it during physical activities and sports.

Question 2

Name the laws of motion.

Solution: The laws of motion, as formulated by Sir Isaac Newton, are:

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 or rod that is capable of rotating about a fixed point. This fixed point around which the rotation occurs 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 primarily used. When you walk, your foot pushes backward on the ground (action), and the ground pushes forward on your body with an equal and opposite force (reaction), propelling you forward.

Question 5

What do you understand by equilibrium?

Solution: Equilibrium refers to a state of balance or a stable condition where the net force and net torque acting on an object are zero. In this state, opposite forces and torques cancel each other out, resulting in no change in the object's motion or orientation.

Question 6

What are the different types of equilibrium?

Solution: There are two main types of equilibrium:

Static Equilibrium: This occurs when an object is at rest and the net force and net torque acting on it are zero. For example, a book lying on a table is in static equilibrium.
Dynamic Equilibrium: This occurs when an object is moving at a constant velocity (both speed and direction) and the net force and net torque acting on it are zero. For example, a runner maintaining a steady pace on a track is in dynamic equilibrium.

Question 7

What is a force?

Solution: A force can be defined as a push or a pull that, when acting upon an object, can change the object's state of motion. According to Newton's second law, force is also mathematically represented as the product of an object's mass and its acceleration (

F = ma

Question 8

What is centre of gravity?

Solution: The center of gravity (CG) is the unique point in a body or a 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.

Question 9

Why do we lean forward while climbing up a hill?

Solution: We lean forward while climbing up a hill to maintain stability. By leaning forward, we shift our center of gravity towards our base of support, which lowers it. A lower center of gravity increases stability, making it easier to counteract the forces acting against us and prevent falling backward.

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 in 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 needs to apply a significant force to overcome their inertia (tendency to remain at rest) and accelerate quickly.

Question 11

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

Solution: When we curl our biceps, a Class III lever is used. In this type of lever, the effort is applied between the fulcrum (the elbow joint) and the resistance (the weight of the forearm and the object being lifted). The biceps muscle provides the effort.

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 generally have greater stability than a thin person of the same height. This is because a larger body mass often results in 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. This position typically involves standing with feet slightly apart, providing a wider base of support compared to standing on one leg, which significantly narrows the base of support and reduces stability.

Common mistakes

Confusing the application of different laws of motion in specific sports actions.
Difficulty in identifying the class of levers in human body movements.
Incomplete understanding of the factors influencing stability and equilibrium.
Not clearly defining terms like force, lever, or center of gravity.

Revision tips

Focus on understanding the definitions of key terms like biomechanics, force, and lever.
Practice identifying which law of motion applies to different sports actions.
Visualize the human body as a system of levers and identify their classes.
Review the factors that affect stability and equilibrium in various physical activities.

Practice MCQs

Q1. What is the primary study area of biomechanics?

Q2. Which of Newton's laws is often referred to as the 'law of reaction'?

Q3. What is a rigid bar capable of rotating about a fixed point called?

Q4. When walking, which law of motion is primarily demonstrated?

Q5. What condition is described as a state of balance where opposite forces cancel each other out?

Frequently asked questions

What is biomechanics?

Biomechanics is the systematic study of the mechanics of biological systems, focusing on the structure and function of the human body in motion.

Which law of motion is relevant when an athlete takes a quick start?

The First Law of Motion, also known as the Law of Inertia, is crucial for an athlete to initiate a quick start by overcoming their state of rest.

What is a lever in the context of the human body?

A lever in the human body is a rigid bar (like a bone) that rotates around a fixed point (the fulcrum or joint) to produce movement, often assisted by a force (muscle).

How does leaning forward help when climbing a hill?

Leaning forward while climbing a hill helps to lower the body's center of gravity, which increases stability and makes it easier to ascend.

What are the two types of equilibrium mentioned?

The two types of equilibrium are static equilibrium, where there is no movement, and dynamic equilibrium, where movement occurs but the body remains balanced.

Which class of lever is used when curling the biceps?

Curling the biceps involves a Class III lever, where the effort is applied between the fulcrum (elbow joint) and the resistance (weight of the forearm and hand).

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