# CBSE Class 11th Physics Notes: Motion in a Straight Line (Part - III)

CBSE Class 11 Physics Notes on Chapter 3, Motion in a Straight Line are available here. The topics covered in these notes are accelerated motion, acceleration & formulas for uniformly accelerated motion along a straight line. These notes are important for CBSE Class 11 Physics exams and other competitive exams like JEE Main, NEET etc.

NCERT based Class 11 Physics chapter notes on Chapter 3, Motion in a Straight Line are available here. These notes are helpful for quick revision of the chapter. This article is continuation of Class 11th Physics Notes: Motion in a Straight Line (**Part – I** & **Part – II**) where basic concepts like Rectilinear motion, Frame of Reference, Path Length, Displacement Speed, Uniform Speed, Variable Speed, Average Speed, Instantaneous Speed, Velocity, Uniform Velocity, Variable Velocity, Average Velocity, Instantaneous Velocity, Uniform Motion in a straight line, Relative Velocity etc. are covered.

Topics covered in this part are accelerated motion, acceleration & formulas for uniformly accelerated motion along a straight line.

The notes are given below:

**Accelerated Motion**

If the velocity of an object keeps changing with time then such motion is said to be in accelerated motion.

*Uniform accelerated motion:*

An object is said to be moving with uniform accelerated motion if the change in velocity of an object in each unit of time is constant.

*Non – Uniform accelerated motion*:

An object is said to be moving with non – uniform accelerated motion if the change in velocity of an object in each unit of time is not constant.

**CBSE Class 11 Physics Syllabus 2017 - 2018**

**Acceleration**

It is defined as the rate of change in velocity of the object.

Acceleration = (change in velocity)/(time taken)

It is a vector quantity and its SI unit is *ms*^{‒2}.

*Uniform Acceleration*

A body is said to be moving with a uniform acceleration if its velocity changes by equal amount in equal intervals of time.

*Variable Acceleration *

A body is said to be moving with a variable acceleration if its velocity changes by unequal amounts in equal intervals of time.

**CBSE Class 11th Physics Notes: Units and Measurement (Part - I)**

*Average Acceleration*

A body moving with variable acceleration then the average acceleration of the body for the given motion is defined as the ratio of the total change in velocity of the body during motion to the total time taken.

Average acceleration = (total change in velocity)/(total time taken) = (Δ*v*/ Δ*t*)

*Instantaneous Acceleration*

The acceleration of the object at a given instant of time or at a given point of motion.

Average acceleration = (total change in velocity)/(total time taken) = (Δ*v*/Δ*t*) [Δ*t*→0].

**Formula for Uniformly Accelerated Motion along a Straight Line**

For objects in uniformly accelerated rectilinear motion, the five quantities, displacement *x*, time taken t, initial velocity *v*_{0}, final velocity *v* and acceleration *a* are related by a set of simple equations called kinematic equations of motion :

**• Velocity time relation:**

*v* = *v*_{o} + *at*

**• Position time relation:**

** x** =

*v*

_{o}

*t*+ ½

*at*

^{2}

**• Position velocity relation:**

*v*^{2} ‒ *v*_{o}^{2} = 2 *a x*

If the position of the object at time *t* = 0 is 0. If the particle starts at *x* = *x*_{0} , *x* in above equations is replaced by (*x* – *x*_{0}).

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