NCERT Class 11 Physics Chapter 3 Notes Motion in a straight Line - Download PDF

# NCERT Class 11 Physics Chapter 3 Notes Motion in a straight Line - Download PDF

Edited By Vishal kumar | Updated on Jan 30, 2024 03:06 PM IST

## Revision Notes for CBSE Class 11 Physics Chapter 3: Motion in a Straight Line - Free PDF Download

Achieving good marks in a chapter is crucial, and a strong command of the material is essential for success. Recognising this, Careers360 experts have carefully developed class 11 Physics chapter 3 notes for Class 11 Physics, focusing on "Motion in a Straight Line."

These Motion in a Straight Line class 11 notes, which correspond to the most recent CBSE Class 11 Physics Syllabus (2023-24), are invaluable for CBSE school exams as well as competitive exams like NEET, JEE Mains, and WBJEE. They are based on the NCERT textbook and provide students with a comprehensive resource.

The Motion in a Straight Line notes class 11 are conveniently available in PDF format, which allows students to access them at any time without an internet connection. These ch 3 physics class 11 notes facilitate a thorough understanding by providing a structured and detailed overview of the chapter, including topics such as displacement, velocity, and equations of motion.

## Rest and Motion

An object is said to be at rest if it remains stationary in relation to a specific frame of reference over time. On the other hand, if an object's position relative to a frame of reference changes over time, it is said to be in motion. A coordinate system to which observers attach coordinates to describe events and observations is referred to as a frame of reference.

## Frame of Reference

A frame of reference is a coordinate system used to describe the position and motion of objects by providing a set of axes relative to an observer's perspective.

According to the frame of reference:

A body is considered in motion if its position changes over time relative to that frame, and it is considered at rest if there is no change in its position within that frame of reference. For instance, when observing a moving vehicle from an external reference frame, it appears to be in motion, while from an internal frame within the vehicle, the surroundings may seem stationary.

## Motion Along a Straight Line

A straight-line motion can be effectively described using only the X-axis of a coordinate system. One-dimensional motion is the movement of a body in a straight line that occurs when only one coordinate of the body's position changes with time.Examples of one-dimensional motion include the motion of a car on a straight road and the motion of a freely falling body.

## Path Length (Distance) Vs. Displacement

Path Length: The distance between two points along a route, a scalar quantity that represents the total length travelled.

Displacement: The change in position of a body, often denoted by ∆x = (x2 - x1), and it is a vector quantity indicating the overall change in position.

In short, path length considers the total distance travelled, whereas displacement considers the net change in position from the initial to the final point while taking direction into account.

• The magnitude of displacement may or may not be equal to the length of the path.

• When an object returns to its original position along a path with a non-zero length, displacement can be zero. Displacement takes into account the change in position regardless of the total distance travelled, as well as the direction of motion.

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## Speed and Velocity

### Speed

Speed is defined as the rate of distance covered with time. Here are some characteristics of speed:

• It is a scalar quantity denoted by the symbol v.
• Dimension: [MoL1T-1]
• Unit: Meter/second (S.I.), cm/second (C.G.S.)

Types of speed

(a) Uniform speed: A particle moves at uniform speed when it covers equal distances in equal intervals of time, regardless of how small those intervals are. For example, a car travels an equal distance of 5 metres per second, indicating a uniform speed of 5 m/s. Uniform speed denotes a constant rate of motion with no acceleration or deceleration during the time intervals specified.

(b) Non-uniform (variable) speed: A particle with non-uniform (variable) speed travels unequal distances in equal time intervals. For example, a car travels 5m in the first second, 8m in the second second, 10m in the third second, 4m in the fourth second, and so on. This variation in distance covered indicates that the particle's speed varies for each one-second interval, confirming that it moves at a variable speed. Variable speed denotes that the rate of motion varies over time.

(c) Average speed: The average speed (Vavg) of a particle for a given interval of time is defined as the ratio of the total distance travelled (d) to the total time taken (t).

(d) Instantaneous speed: It is the speed of a particle at a specific point in time. When we talk about "speed," we usually mean instantaneous speed.

### Velocity

Velocity is defined as the rate of change of position or the rate of displacement with time.

• It is a vector quantity having the symbol v.
• Dimension of velocity: [M0L1T-1]
• Unit: Meter/second (S.I.), cm/second (C.G.S.)

Types of Velocity

(1) Uniform velocity: The condition in which both the magnitude and direction of an object's velocity remain constant is referred to as uniform velocity. This occurs when the particle continues to move in the same straight line without changing direction. To put it another way, a particle with uniform velocity must travel at a constant speed along a straight path with no change in motion.

(2) Non-uniform velocity: Changes in the magnitude or direction of the velocity, or both, characterise non-uniform velocity. The particle's speed and/or direction of motion may change in this scenario. Non-uniform velocity indicates that the object is not moving in a straight line at a constant speed, but rather has variations in its motion over time.

(c) Average velocity: It is defined as the ratio of the body's displacement to the time it takes.

(d) Instantaneous velocity: Instantaneous velocity is defined as the rate of change of the position vector of a particle with respect to time at a specific instant.

## Acceleration

Acceleration is defined as the time rate at which an object's velocity changes. it tells us how quickly and in which direction an object's velocity is changing. It is expressed in acceleration units such as metres per second squared.

• It is a vector quantity with the same direction as the change in velocity (not the velocity itself).
• Dimension of acceleration: [M0L1T-2]
• Units: [meter(m)/second2(s2)] in (S.I. ), [centimeter(cm)/second2(s2)] in (C.G.S.).

Types of Acceleration

(a) Uniform acceleration: Uniform acceleration refers to a situation in which both the magnitude and direction of the acceleration of a body remain constant during its motion.

(b) Non-uniform acceleration: A body is said to have non-uniform acceleration if there are changes in either the magnitude or direction of acceleration, or both, during its motion.

(c) Average acceleration: The average acceleration of an object is defined as the change in velocity per unit time.

Position-Time, Velocity-Time, and Acceleration-Time Graph

 Parameters P-T Graph V-T Graph A-T Graph X and Y axis Time and Position Time and Velocity Time and Acceleration Slope It gives the velocity of an object It gives the acceleration of an object. It gives push of a moving object. Straight slope It gives uniform velocity It gives uniform acceleration It gives uniform jerk Curvy Slope Change in velocity Change in acceleration Change in the amount of push

PT Graph

VT Graph

## Kinematic Equations for Uniformly Accelerated Motion

There are three kinematic equations of rectilinear motion for a constant acceleration.

 Position of the object at time t = 0 is 0 Position of the object at time t = 0 is x0 v = v0 + at v = v0 + at x = v0t + ½ at2 x = x0+ v0t + ½ at2 v2 = v02 + 2ax v2 = v02 + 2a(x-x0)

## Relative Velocity

It is defined as the velocity of an object relative to some other object which might be stationary, moving slowly, moving with the same velocity, moving with higher velocity or moving in opposite direction.

If the initial position of two objects A and B are XA(0) and XB(0), the position at time t will be,

XA(t)= XA(0)+VAt

XB(t)= XB(0)+VBt

Displacement from object A to B, [XB(0)-XA(0)]+(VB-VA)

Velocity of B relative to A = VBA=VB-VA

Velocity of A relative to B =VAB=VA-VB

## How Motion in a Straight Line Class 11 Notes is Important

Motion in a Straight Line notes Class 11 is important for several reasons:

• Understanding motion in a straight line serves as a foundation for more complex concepts in physics, particularly in the study of kinematics and dynamics.
• It introduces students to fundamental concepts such as displacement, velocity, and acceleration, as well as the relationships between these quantities. These principles are critical for understanding many aspects of physics.
• Many real-world phenomena involve straight-line motion. This topic's principles can be used to analyse and comprehend the motion of objects in everyday situations.
• Studying motion in a straight line entails solving kinematics-related mathematical problems. This aids in the development of problem-solving and analytical abilities.
• A solid understanding of motion in a straight line is essential for students planning to pursue further studies in physics or related fields. It serves as a foundation for more advanced mechanics topics.
• The principles of motion are used in many technological applications. Understanding these principles is critical for careers in engineering, technology, and other applied sciences.

## Key Features of Physics Class 11 Chapter 3 Notes PDF

• These Motion in a Straight Line notes class 11 are written in alignment with the CBSE Class 11 Physics Syllabus, ensuring that you cover all of the important topics.
• The CBSE class 11 physics ch 3 notes are written in simple language to help you understand difficult physics concepts more easily.
• Physics class 11 chapter 3 notes pdf summarises all of the chapter's key points, formulas, and principles, providing you with a comprehensive overview of the chapter.
• Use these notes as quick revision tools before exams to ensure you have a solid understanding of the chapter.
• You can easily access the Motion in a Straight Line class 11 notes because they are free in both digital and print formats, making your study routine more flexible.
• These notes are useful not only for regular exams, but also for preparing for competitive exams such as VITEEE, BITSAT, JEE Main, NEET, and others, as they cover the core concepts of the Class 11 Physics Syllabus.

## Significance of NCERT Class 11 Physics Chapter 3 Notes

Motion in a straight line 11 notes will be helpful to revise the chapter and to get an idea about the main topics covered in the chapter. Also, this NCERT Class 11 Physics chapter 3 notes are useful to cover the main topics of the Class 11 CBSE Physics Syllabus and also for competitive exams like VITEEE, BITSAT, JEE Main, NEET, etc. Class 11 Physics chapter 3 notes pdf download can be used to prepare in offline mode.

## NCERT Class 12 Notes Chapter-Wise

 NCERT Class 11 Physics Chapter 1 Notes NCERT Class 11 Physics Chapter 2 Notes NCERT Class 11 Physics Chapter 3 Notes NCERT Class 11 Physics Chapter 4 Notes NCERT Class 11 Physics Chapter 5 Notes NCERT Class 11 Physics Chapter 6 Notes NCERT Class 11 Physics Chapter 7 Notes NCERT Class 11 Physics Chapter 8 Notes NCERT Class 11 Physics Chapter 9 Notes NCERT Class 11 Physics Chapter 10 Notes NCERT Class 11 Physics Chapter 11 Notes NCERT Class 11 Physics Chapter 12 Notes NCERT Class 11 Physics Chapter 13 Notes NCERT Class 11 Physics Chapter 14 Notes NCERT Class 11 Physics Chapter 15 Notes

### Subject Wise NCERT Solutions

 NCERT Books for Class 11 NCERT Syllabus for Class 11

1. What are the main derivations covered in the Motion in a straight line Class 11 notes.

No derivations are covered in the NCERT notes for Class 11 Physics chapter 3. This NCERT note is a brief of the main topics and equations covered in the chapter and can be used for revising the Motion in a straight line.

2. According to Motion in a straight line, two balls of different masses are thrown vertically upward with the same initial speed. Which one will rise to a greater height?

According to Motion in a straight line, when two balls of different masses are thrown vertically upward with the same initial speed, both of them will rise to a greater height.

3. What is the shape of the displacement time graph for uniform linear motion according to the Class 11 Physics chapter 3 notes?

The shape of the displacement time graph for uniform linear motion is a straight line inclined to the time axis (x-axis).

4. What is instantaneous velocity according to the NCERT Class 11 Physics chapter 3 notes and Motion in a straight line, Class 11 notes?

According to the NCERT Class 11 Physics chapter 3 notes instantaneous velocity describes how fast an object is moving at different instants of time in a given time interval.

v=dx/dt

5. What is instantaneous acceleration according to the NCERT Class 11 Physics chapter 3 notes?

According to the NCERT Class 11 Physics chapter 3 notes and Class 11 Motion in a straight line, instantaneous acceleration is defined as the acceleration at different instants of time. Acceleration at an instant is the slope of tangent to the v-t curve at that instant.

a=dv/dt

6. Is physics class 11 chapter 3 notes pdf important for JEE?

Yes, Physics Class 11 Chapter 3 notes in PDF format are important for JEE preparation as they cover fundamental concepts aligned with the JEE syllabus.

7. What is the SI unit of velocity, speed and acceleration?

The SI (International System of Units) units for velocity, speed, and acceleration are as follows:

• Velocity: Meter per second (m/s)
• Speed: Meter per second (m/s)
• Acceleration: Meter per second squared (m/s²)
8. What is Retardation?

Retardation refers to the decrease in velocity or the negative acceleration of an object, indicating a slowing down of its motion.

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A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

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 Option 1) 2.45×10−3 kg Option 2)  6.45×10−3 kg Option 3)  9.89×10−3 kg Option 4) 12.89×10−3 kg

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In the reaction,

 Option 1)   at STP  is produced for every mole   consumed Option 2)   is consumed for ever      produced Option 3) is produced regardless of temperature and pressure for every mole Al that reacts Option 4) at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, will contain 0.25 mole of oxygen atoms?

 Option 1) 0.02 Option 2) 3.125 × 10-2 Option 3) 1.25 × 10-2 Option 4) 2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

 Option 1) decrease twice Option 2) increase two fold Option 3) remain unchanged Option 4) be a function of the molecular mass of the substance.

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 Option 1) Molality Option 2) Weight fraction of solute Option 3) Fraction of solute present in water Option 4) Mole fraction.

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 Option 1) twice that in 60 g carbon Option 2) 6.023 × 1022 Option 3) half that in 8 g He Option 4) 558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

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