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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.
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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.
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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.
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.
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: 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 = (x_{2} - x_{1}), 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.
Speed is defined as the rate of distance covered with time. Here are some characteristics of speed:
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 (V_{avg}) 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 is defined as the rate of change of position or the rate of displacement with time.
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 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.
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
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 x_{0} |
v = v_{0 }+ at | v = v_{0} + at |
x = v_{0}t + ½ at^{2} | x = x_{0}+ v_{0}t + ½ at^{2} |
v2 = v_{0}^{2} + 2ax | v^{2} = v_{0}^{2} + 2a(x-x_{0}) |
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 X_{A}(0) and X_{B}(0), the position at time t will be,
X_{A}(t)= X_{A}(0)+V_{A}t
X_{B}(t)= X_{B}(0)+V_{B}t
Displacement from object A to B, [X_{B}(0)-X_{A}(0)]+(V_{B}-V_{A})
Velocity of B relative to A = V_{BA}=V_{B}-V_{A}
Velocity of A relative to B =V_{AB}=V_{A}-V_{B}
Motion in a Straight Line notes Class 11 is important for several reasons:
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.
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.
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.
The shape of the displacement time graph for uniform linear motion is a straight line inclined to the time axis (x-axis).
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
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
These topics can also be downloaded from Motion in a straight line Class 11 notes pdf download.
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.
The SI (International System of Units) units for velocity, speed, and acceleration are as follows:
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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